The Father of Genetics<\/h1>\n<\/div>\nMendel did experiments with pea plants to show how traits such as seed shape and flower colour are inherited. Based on his research, he developed his two well known laws of inheritance: the [pb_glossary id=\"1526\"]law of segregation[\/pb_glossary] and the [pb_glossary id=\"1524\"]law of independent assortment[\/pb_glossary]. When Mendel died in 1884, his work was still virtually unknown. In 1900, three other researchers working independently came to the same conclusions that Mendel had drawn almost half a century earlier. Only then was Mendel's work rediscovered.\n\nMendel knew nothing about genes, because they\u00a0were discovered after his death. He did think, however, that some type of \"factors\" controlled traits, and that those \"factors\" were passed from parents to offspring. We now call these \"factors\" genes.\u00a0[pb_glossary id=\"2075\"]Mendel's laws\u00a0of inheritance[\/pb_glossary], now expressed in terms of genes,\u00a0form the basis of\u00a0[pb_glossary id=\"1484\"]genetics[\/pb_glossary]<\/strong>, the science of heredity. For this reason, Mendel is often called the father of genetics.\n\nThe Language of Genetics<\/h1>\n<\/div>\nToday, we know that traits of organisms are controlled by [pb_glossary id=\"1226\"]genes[\/pb_glossary] on\u00a0[pb_glossary id=\"1275\"]chromosomes[\/pb_glossary]. To talk about inheritance in terms of genes and chromosomes, you need to know the language of genetics.\u00a0The terms below serve\u00a0as\u00a0a good starting point. They are illustrated in the\u00a0figure\u00a0that follows.\n\n \t- A\u00a0[pb_glossary id=\"1226\"]gene[\/pb_glossary]<\/strong> is the part of a [pb_glossary id=\"1275\"]chromosome[\/pb_glossary] that contains the\u00a0genetic code\u00a0for a given\u00a0[pb_glossary id=\"1373\"]protein[\/pb_glossary]. For example, in\u00a0pea plants, a given gene might code for flower\u00a0colour.<\/li>\n \t
- The position of a given gene on a chromosome is called its\u00a0[pb_glossary id=\"1531\"]locus[\/pb_glossary] <\/strong>(plural, loci). A gene might be located near the center, or at one end or the other of a [pb_glossary id=\"1275\"]chromosome[\/pb_glossary].<\/li>\n \t
- A given gene may have different normal versions, which are called [pb_glossary id=\"1190\"]alleles[\/pb_glossary]<\/strong>.<\/strong> For example, in\u00a0pea plants, there is a purple-flower allele (B) and a white-flower allele (b) for the flower-colour\u00a0gene. Different\u00a0alleles account for much of the variation in the traits of organisms, including people.<\/li>\n \t
- In sexually reproducing organisms, each individual has two copies of each type of chromosome. Paired\u00a0chromosomes\u00a0of the same type are called\u00a0[pb_glossary id=\"1270\"]homologous<\/strong>\u00a0<\/strong>chromosomes<\/strong>[\/pb_glossary]. They are about the same size and shape, and they have all the same genes at the same loci.<\/li>\n<\/ul>\n[caption id=\"attachment_333\" align=\"aligncenter\" width=\"500\"]
![\"\"](\"https:\/\/pressbooks.bccampus.ca\/testclone1\/wp-content\/uploads\/sites\/1601\/2022\/01\/f-d_56cb7ecdd193e58369e5f34a1b55594b30afa8c99312e8001ee5b70bIMAGE_THUMB_POSTCARD_TINYIMAGE_THUMB_POSTCARD_TINY.png\")
Figure 5.11.2 Chromosome, Gene, Locus, and Allele. This diagram shows how the concepts of chromosome, gene, locus, and allele are related. What is the difference between a gene and a locus? Between a gene and an allele?<\/em>[\/caption]\n\n\nGenotype<\/h2>\n<\/div>\nWhen\u00a0[pb_glossary id=\"1624\"]sexual reproduction[\/pb_glossary]\u00a0occurs, sex\u00a0cells\u00a0(called [pb_glossary id=\"1477\"]gametes[\/pb_glossary]) unite during\u00a0[pb_glossary id=\"1470\"]fertilization[\/pb_glossary]\u00a0to form a single cell called a\u00a0[pb_glossary id=\"1685\"]zygote[\/pb_glossary]<\/strong>. The zygote inherits two of each type of chromosome, with one chromosome of each type coming from the father, and the other coming from the mother. Because [pb_glossary id=\"1270\"]homologous chromosomes[\/pb_glossary] have the same genes at the same loci, each individual also inherits two copies of each gene. The two copies may be the same allele or different\u00a0[pb_glossary id=\"1190\"]alleles[\/pb_glossary]. The alleles an individual inherits for a given gene make up the individual\u2019s\u00a0[pb_glossary id=\"1485\"]genotype[\/pb_glossary]<\/strong>. \u00a0As shown in Table 5.11.1, an organism with two of the same allele (for example, BB<\/em>\u00a0or\u00a0bb<\/em>) is called a\u00a0[pb_glossary id=\"1501\"]homozygote[\/pb_glossary]<\/strong>. An organism with two different alleles (in this example,\u00a0Bb<\/em>) is called a\u00a0[pb_glossary id=\"1492\"]heterozygote[\/pb_glossary]<\/strong>.\n\nTable 5.11.1\u00a0<\/strong>\n\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em>\n\n![\"Illustrates](\"https:\/\/pressbooks.bccampus.ca\/testclone1\/wp-content\/uploads\/sites\/1601\/2022\/01\/Untitled.png\")
\n\n \n\nPhenotype<\/span>\n\nThe expression of an organism\u2019s genotype is referred to as its\u00a0[pb_glossary id=\"1583\"]phenotype[\/pb_glossary]<\/strong>, and it refers to the organism\u2019s traits, such as purple or white flowers in pea plants. As you can see from Table 5.11.1, different genotypes may produce the same phenotype. In this example, both BB<\/em>\u00a0and\u00a0Bb<\/em>\u00a0genotypes produce plants with the same phenotype, purple flowers. Why does this happen? In a\u00a0Bb<\/em>\u00a0heterozygote, only the\u00a0B<\/em>\u00a0allele is expressed, so the\u00a0b <\/em>allele doesn\u2019t influence the phenotype. In general, when only one of two alleles is expressed in the phenotype, the expressed allele is called\u00a0[pb_glossary id=\"1451\"]dominant[\/pb_glossary],<\/strong>\u00a0and the allele that isn\u2019t expressed is called\u00a0[pb_glossary id=\"1605\"]recessive[\/pb_glossary].<\/strong>\n\nThe terms\u00a0dominant<\/em>\u00a0and\u00a0recessive<\/em> may also be used to refer to phenotypic traits. For example, purple flower colour in pea plants is a dominant trait. It shows up in the phenotype whenever a plant inherits even one dominant allele for the trait. Similarly, white flower colour is a recessive trait. Like other recessive traits, it shows up in the phenotype only when a plant inherits two<\/em>\u00a0recessive alleles for the trait.\n\n5.11 Summary<\/span><\/h1>\n<\/header>\n\n\n \t- Mendel's laws\u00a0of inheritance, now expressed in terms of [pb_glossary id=\"1226\"]genes[\/pb_glossary], form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n \t
- A gene is the part of a [pb_glossary id=\"1275\"]chromosome[\/pb_glossary] that codes for a given\u00a0[pb_glossary id=\"1373\"]protein[\/pb_glossary]. The position of a gene on a chromosome is its [pb_glossary id=\"1531\"]locus[\/pb_glossary].\u00a0\u00a0A given gene may have different versions, called [pb_glossary id=\"1190\"]alleles[\/pb_glossary].\u00a0Paired chromosomes of the same type are called [pb_glossary id=\"1270\"]homologous chromosomes[\/pb_glossary]. They have the same size and shape, and they have the same genes at the same [pb_glossary id=\"1531\"]loci[\/pb_glossary].<\/li>\n \t
- The alleles an individual inherits for a given gene make up the individual's [pb_glossary id=\"1485\"]genotype[\/pb_glossary]. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n \t
- The expression of an organism's genotype is referred to as its [pb_glossary id=\"1583\"]phenotype[\/pb_glossary]. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n5.11 Review Questions<\/span><\/h1>\n<\/header>\n\n\n \t- Define genetics.<\/li>\n \t
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n \t
- [h5p id=\"66\"]<\/li>\n \t
- Imagine that there are two alleles, R <\/em>and\u00a0r<\/em>, for a given gene.\u00a0R<\/em>\u00a0is dominant to\u00a0r<\/em>. Answer the following questions about this gene:\n
\n \t- What are the possible homozygous and heterozygous genotypes?<\/li>\n \t
- Which genotype or genotypes express the dominant\u00a0R\u00a0<\/em>phenotype? Explain your answer.<\/li>\n \t
- Are R <\/em>and\u00a0r<\/em>\u00a0on different loci? Why or why not?<\/li>\n \t
- Can R <\/em>and\u00a0r<\/em>\u00a0be on the same exact chromosome? Why or why not? If not, where are they located?<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<\/div>\n<\/div>\n
\n5.11 Explore More<\/span><\/h1>\n<\/header>\n\n\nhttps:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE\nAlleles and Genes, Amoeba Sisters, 2018.<\/p>\nhttps:\/\/www.youtube.com\/watch?v=OaovnS7BAoc\n
Genotypes and Phenotypes, Bozeman Science, 2011.<\/p>\n\n<\/div>\n<\/div>\n \n
Attributions<\/h2>\nFigure 5.11.1<\/strong>\n\nFather holding his baby boy with matching haircut<\/a> [photo] by Kelly Sikkema<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\n\nFigure 5.11.2<\/strong>\n\nChromosome, Gene, Locus, and Allele<\/a>\u00a0by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\n\n![\"\"](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/logo_ck12.png\")
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span>![\"CK-12](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/icon_licence.png\" "\\"CK-12")
<\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\n\nTable 5.11.1<\/strong>\n\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em> by Christine Miller is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\nReferences<\/h2>\n
Amoeba Sisters. (2018, February 1). Alleles and genes. YouTube. https:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE&feature=youtu.be<\/p>\n
Bozeman Science. (2011, August 4). Genotypes and phenotypes. YouTube. https:\/\/www.youtube.com\/watch?v=OaovnS7BAoc&feature=youtu.be<\/p>\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 2 Chromosome, gene, locus, and allele [digital image]. In CK-12 College Human Biology\u00a0<\/em>(Section 5.10) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-human-biology\/section\/5.9\/<\/p>\n \n\n ","rendered":"Created by: CK-12\/Adapted by Christine Miller<\/p>\n![\"Image](\"https:\/\/pressbooks.bccampus.ca\/testclone1\/wp-content\/uploads\/sites\/1601\/2019\/06\/kelly-sikkema-FqqaJI9OxMI-unsplash-scaled-1.jpg\")
Figure 5.11.1 Like Father, Like Son.<\/em><\/figcaption><\/figure>\nLike Father, Like Son<\/h1>\n
This father-son duo share some similarities.\u00a0 The shape of their faces and their facial features look very similar. If you saw them together, you might well guess that they are father and son. People have long known that the characteristics of living things are similar between parents and their offspring. However, it wasn\u2019t until the experiments of Gregor Mendel\u00a0that scientists understood\u00a0how<\/em>\u00a0those traits are inherited.<\/p>\n\nThe Father of Genetics<\/h1>\n<\/div>\n
Mendel did experiments with pea plants to show how traits such as seed shape and flower colour are inherited. Based on his research, he developed his two well known laws of inheritance: the law of segregation<\/a> and the law of independent assortment<\/a>. When Mendel died in 1884, his work was still virtually unknown. In 1900, three other researchers working independently came to the same conclusions that Mendel had drawn almost half a century earlier. Only then was Mendel’s work rediscovered.<\/p>\nMendel knew nothing about genes, because they\u00a0were discovered after his death. He did think, however, that some type of “factors” controlled traits, and that those “factors” were passed from parents to offspring. We now call these “factors” genes.\u00a0Mendel's laws\u00a0of inheritance<\/a>, now expressed in terms of genes,\u00a0form the basis of\u00a0genetics<\/a><\/strong>, the science of heredity. For this reason, Mendel is often called the father of genetics.<\/p>\n\nThe Language of Genetics<\/h1>\n<\/div>\n
Today, we know that traits of organisms are controlled by genes<\/a> on\u00a0chromosomes<\/a>. To talk about inheritance in terms of genes and chromosomes, you need to know the language of genetics.\u00a0The terms below serve\u00a0as\u00a0a good starting point. They are illustrated in the\u00a0figure\u00a0that follows.<\/p>\n\n- A\u00a0gene<\/a><\/strong> is the part of a chromosome<\/a> that contains the\u00a0genetic code\u00a0for a given\u00a0protein<\/a>. For example, in\u00a0pea plants, a given gene might code for flower\u00a0colour.<\/li>\n
- The position of a given gene on a chromosome is called its\u00a0locus<\/a> <\/strong>(plural, loci). A gene might be located near the center, or at one end or the other of a chromosome<\/a>.<\/li>\n
- A given gene may have different normal versions, which are called alleles<\/a><\/strong>.<\/strong> For example, in\u00a0pea plants, there is a purple-flower allele (B) and a white-flower allele (b) for the flower-colour\u00a0gene. Different\u00a0alleles account for much of the variation in the traits of organisms, including people.<\/li>\n
- In sexually reproducing organisms, each individual has two copies of each type of chromosome. Paired\u00a0chromosomes\u00a0of the same type are called\u00a0homologous<\/strong>\u00a0<\/strong>chromosomes<\/strong><\/a>. They are about the same size and shape, and they have all the same genes at the same loci.<\/li>\n<\/ul>\n
Figure 5.11.2 Chromosome, Gene, Locus, and Allele. This diagram shows how the concepts of chromosome, gene, locus, and allele are related. What is the difference between a gene and a locus? Between a gene and an allele?<\/em><\/figcaption><\/figure>\n\nGenotype<\/h2>\n<\/div>\n
When\u00a0sexual reproduction<\/a>\u00a0occurs, sex\u00a0cells\u00a0(called gametes<\/a>) unite during\u00a0fertilization<\/a>\u00a0to form a single cell called a\u00a0zygote<\/a><\/strong>. The zygote inherits two of each type of chromosome, with one chromosome of each type coming from the father, and the other coming from the mother. Because homologous chromosomes<\/a> have the same genes at the same loci, each individual also inherits two copies of each gene. The two copies may be the same allele or different\u00a0alleles<\/a>. The alleles an individual inherits for a given gene make up the individual\u2019s\u00a0genotype<\/a><\/strong>. \u00a0As shown in Table 5.11.1, an organism with two of the same allele (for example, BB<\/em>\u00a0or\u00a0bb<\/em>) is called a\u00a0homozygote<\/a><\/strong>. An organism with two different alleles (in this example,\u00a0Bb<\/em>) is called a\u00a0heterozygote<\/a><\/strong>.<\/p>\nTable 5.11.1\u00a0<\/strong><\/p>\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em><\/p>\n<\/p>\n
<\/p>\n
Phenotype<\/span><\/p>\nThe expression of an organism\u2019s genotype is referred to as its\u00a0phenotype<\/a><\/strong>, and it refers to the organism\u2019s traits, such as purple or white flowers in pea plants. As you can see from Table 5.11.1, different genotypes may produce the same phenotype. In this example, both BB<\/em>\u00a0and\u00a0Bb<\/em>\u00a0genotypes produce plants with the same phenotype, purple flowers. Why does this happen? In a\u00a0Bb<\/em>\u00a0heterozygote, only the\u00a0B<\/em>\u00a0allele is expressed, so the\u00a0b <\/em>allele doesn\u2019t influence the phenotype. In general, when only one of two alleles is expressed in the phenotype, the expressed allele is called\u00a0dominant<\/a>,<\/strong>\u00a0and the allele that isn\u2019t expressed is called\u00a0recessive<\/a>.<\/strong><\/p>\nThe terms\u00a0dominant<\/em>\u00a0and\u00a0recessive<\/em> may also be used to refer to phenotypic traits. For example, purple flower colour in pea plants is a dominant trait. It shows up in the phenotype whenever a plant inherits even one dominant allele for the trait. Similarly, white flower colour is a recessive trait. Like other recessive traits, it shows up in the phenotype only when a plant inherits two<\/em>\u00a0recessive alleles for the trait.<\/p>\n\n\n5.11 Summary<\/span><\/h1>\n<\/header>\n\n\n- Mendel’s laws\u00a0of inheritance, now expressed in terms of genes<\/a>, form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n
- A gene is the part of a chromosome<\/a> that codes for a given\u00a0protein<\/a>. The position of a gene on a chromosome is its locus<\/a>.\u00a0\u00a0A given gene may have different versions, called alleles<\/a>.\u00a0Paired chromosomes of the same type are called homologous chromosomes<\/a>. They have the same size and shape, and they have the same genes at the same loci<\/a>.<\/li>\n
- The alleles an individual inherits for a given gene make up the individual’s genotype<\/a>. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n
- The expression of an organism’s genotype is referred to as its phenotype<\/a>. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.11 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define genetics.<\/li>\n
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n
- \n\n
The Language of Genetics<\/h1>\n<\/div>\nToday, we know that traits of organisms are controlled by [pb_glossary id=\"1226\"]genes[\/pb_glossary] on\u00a0[pb_glossary id=\"1275\"]chromosomes[\/pb_glossary]. To talk about inheritance in terms of genes and chromosomes, you need to know the language of genetics.\u00a0The terms below serve\u00a0as\u00a0a good starting point. They are illustrated in the\u00a0figure\u00a0that follows.\n\n \t- A\u00a0[pb_glossary id=\"1226\"]gene[\/pb_glossary]<\/strong> is the part of a [pb_glossary id=\"1275\"]chromosome[\/pb_glossary] that contains the\u00a0genetic code\u00a0for a given\u00a0[pb_glossary id=\"1373\"]protein[\/pb_glossary]. For example, in\u00a0pea plants, a given gene might code for flower\u00a0colour.<\/li>\n \t
- The position of a given gene on a chromosome is called its\u00a0[pb_glossary id=\"1531\"]locus[\/pb_glossary] <\/strong>(plural, loci). A gene might be located near the center, or at one end or the other of a [pb_glossary id=\"1275\"]chromosome[\/pb_glossary].<\/li>\n \t
- A given gene may have different normal versions, which are called [pb_glossary id=\"1190\"]alleles[\/pb_glossary]<\/strong>.<\/strong> For example, in\u00a0pea plants, there is a purple-flower allele (B) and a white-flower allele (b) for the flower-colour\u00a0gene. Different\u00a0alleles account for much of the variation in the traits of organisms, including people.<\/li>\n \t
- In sexually reproducing organisms, each individual has two copies of each type of chromosome. Paired\u00a0chromosomes\u00a0of the same type are called\u00a0[pb_glossary id=\"1270\"]homologous<\/strong>\u00a0<\/strong>chromosomes<\/strong>[\/pb_glossary]. They are about the same size and shape, and they have all the same genes at the same loci.<\/li>\n<\/ul>\n[caption id=\"attachment_333\" align=\"aligncenter\" width=\"500\"] Figure 5.11.2 Chromosome, Gene, Locus, and Allele. This diagram shows how the concepts of chromosome, gene, locus, and allele are related. What is the difference between a gene and a locus? Between a gene and an allele?<\/em>[\/caption]\n\n\n
Genotype<\/h2>\n<\/div>\nWhen\u00a0[pb_glossary id=\"1624\"]sexual reproduction[\/pb_glossary]\u00a0occurs, sex\u00a0cells\u00a0(called [pb_glossary id=\"1477\"]gametes[\/pb_glossary]) unite during\u00a0[pb_glossary id=\"1470\"]fertilization[\/pb_glossary]\u00a0to form a single cell called a\u00a0[pb_glossary id=\"1685\"]zygote[\/pb_glossary]<\/strong>. The zygote inherits two of each type of chromosome, with one chromosome of each type coming from the father, and the other coming from the mother. Because [pb_glossary id=\"1270\"]homologous chromosomes[\/pb_glossary] have the same genes at the same loci, each individual also inherits two copies of each gene. The two copies may be the same allele or different\u00a0[pb_glossary id=\"1190\"]alleles[\/pb_glossary]. The alleles an individual inherits for a given gene make up the individual\u2019s\u00a0[pb_glossary id=\"1485\"]genotype[\/pb_glossary]<\/strong>. \u00a0As shown in Table 5.11.1, an organism with two of the same allele (for example, BB<\/em>\u00a0or\u00a0bb<\/em>) is called a\u00a0[pb_glossary id=\"1501\"]homozygote[\/pb_glossary]<\/strong>. An organism with two different alleles (in this example,\u00a0Bb<\/em>) is called a\u00a0[pb_glossary id=\"1492\"]heterozygote[\/pb_glossary]<\/strong>.\n\nTable 5.11.1\u00a0<\/strong>\n\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em>\n\n\n\n \n\nPhenotype<\/span>\n\nThe expression of an organism\u2019s genotype is referred to as its\u00a0[pb_glossary id=\"1583\"]phenotype[\/pb_glossary]<\/strong>, and it refers to the organism\u2019s traits, such as purple or white flowers in pea plants. As you can see from Table 5.11.1, different genotypes may produce the same phenotype. In this example, both BB<\/em>\u00a0and\u00a0Bb<\/em>\u00a0genotypes produce plants with the same phenotype, purple flowers. Why does this happen? In a\u00a0Bb<\/em>\u00a0heterozygote, only the\u00a0B<\/em>\u00a0allele is expressed, so the\u00a0b <\/em>allele doesn\u2019t influence the phenotype. In general, when only one of two alleles is expressed in the phenotype, the expressed allele is called\u00a0[pb_glossary id=\"1451\"]dominant[\/pb_glossary],<\/strong>\u00a0and the allele that isn\u2019t expressed is called\u00a0[pb_glossary id=\"1605\"]recessive[\/pb_glossary].<\/strong>\n\nThe terms\u00a0dominant<\/em>\u00a0and\u00a0recessive<\/em> may also be used to refer to phenotypic traits. For example, purple flower colour in pea plants is a dominant trait. It shows up in the phenotype whenever a plant inherits even one dominant allele for the trait. Similarly, white flower colour is a recessive trait. Like other recessive traits, it shows up in the phenotype only when a plant inherits two<\/em>\u00a0recessive alleles for the trait.\n\n5.11 Summary<\/span><\/h1>\n<\/header>\n\n\n \t- Mendel's laws\u00a0of inheritance, now expressed in terms of [pb_glossary id=\"1226\"]genes[\/pb_glossary], form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n \t
- A gene is the part of a [pb_glossary id=\"1275\"]chromosome[\/pb_glossary] that codes for a given\u00a0[pb_glossary id=\"1373\"]protein[\/pb_glossary]. The position of a gene on a chromosome is its [pb_glossary id=\"1531\"]locus[\/pb_glossary].\u00a0\u00a0A given gene may have different versions, called [pb_glossary id=\"1190\"]alleles[\/pb_glossary].\u00a0Paired chromosomes of the same type are called [pb_glossary id=\"1270\"]homologous chromosomes[\/pb_glossary]. They have the same size and shape, and they have the same genes at the same [pb_glossary id=\"1531\"]loci[\/pb_glossary].<\/li>\n \t
- The alleles an individual inherits for a given gene make up the individual's [pb_glossary id=\"1485\"]genotype[\/pb_glossary]. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n \t
- The expression of an organism's genotype is referred to as its [pb_glossary id=\"1583\"]phenotype[\/pb_glossary]. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n5.11 Review Questions<\/span><\/h1>\n<\/header>\n\n\n \t- Define genetics.<\/li>\n \t
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n \t
- [h5p id=\"66\"]<\/li>\n \t
- Imagine that there are two alleles, R <\/em>and\u00a0r<\/em>, for a given gene.\u00a0R<\/em>\u00a0is dominant to\u00a0r<\/em>. Answer the following questions about this gene:\n
\n \t- What are the possible homozygous and heterozygous genotypes?<\/li>\n \t
- Which genotype or genotypes express the dominant\u00a0R\u00a0<\/em>phenotype? Explain your answer.<\/li>\n \t
- Are R <\/em>and\u00a0r<\/em>\u00a0on different loci? Why or why not?<\/li>\n \t
- Can R <\/em>and\u00a0r<\/em>\u00a0be on the same exact chromosome? Why or why not? If not, where are they located?<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<\/div>\n<\/div>\n
\n5.11 Explore More<\/span><\/h1>\n<\/header>\n\n\nhttps:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE\nAlleles and Genes, Amoeba Sisters, 2018.<\/p>\nhttps:\/\/www.youtube.com\/watch?v=OaovnS7BAoc\n
Genotypes and Phenotypes, Bozeman Science, 2011.<\/p>\n\n<\/div>\n<\/div>\n \n
Attributions<\/h2>\nFigure 5.11.1<\/strong>\n\nFather holding his baby boy with matching haircut<\/a> [photo] by Kelly Sikkema<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\n\nFigure 5.11.2<\/strong>\n\nChromosome, Gene, Locus, and Allele<\/a>\u00a0by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\n\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\n\nTable 5.11.1<\/strong>\n\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em> by Christine Miller is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\nReferences<\/h2>\n
Amoeba Sisters. (2018, February 1). Alleles and genes. YouTube. https:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE&feature=youtu.be<\/p>\n
Bozeman Science. (2011, August 4). Genotypes and phenotypes. YouTube. https:\/\/www.youtube.com\/watch?v=OaovnS7BAoc&feature=youtu.be<\/p>\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 2 Chromosome, gene, locus, and allele [digital image]. In CK-12 College Human Biology\u00a0<\/em>(Section 5.10) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-human-biology\/section\/5.9\/<\/p>\n \n\n ","rendered":"Created by: CK-12\/Adapted by Christine Miller<\/p>\nFigure 5.11.1 Like Father, Like Son.<\/em><\/figcaption><\/figure>\nLike Father, Like Son<\/h1>\n
This father-son duo share some similarities.\u00a0 The shape of their faces and their facial features look very similar. If you saw them together, you might well guess that they are father and son. People have long known that the characteristics of living things are similar between parents and their offspring. However, it wasn\u2019t until the experiments of Gregor Mendel\u00a0that scientists understood\u00a0how<\/em>\u00a0those traits are inherited.<\/p>\n\nThe Father of Genetics<\/h1>\n<\/div>\n
Mendel did experiments with pea plants to show how traits such as seed shape and flower colour are inherited. Based on his research, he developed his two well known laws of inheritance: the law of segregation<\/a> and the law of independent assortment<\/a>. When Mendel died in 1884, his work was still virtually unknown. In 1900, three other researchers working independently came to the same conclusions that Mendel had drawn almost half a century earlier. Only then was Mendel’s work rediscovered.<\/p>\nMendel knew nothing about genes, because they\u00a0were discovered after his death. He did think, however, that some type of “factors” controlled traits, and that those “factors” were passed from parents to offspring. We now call these “factors” genes.\u00a0Mendel's laws\u00a0of inheritance<\/a>, now expressed in terms of genes,\u00a0form the basis of\u00a0genetics<\/a><\/strong>, the science of heredity. For this reason, Mendel is often called the father of genetics.<\/p>\n\nThe Language of Genetics<\/h1>\n<\/div>\n
Today, we know that traits of organisms are controlled by genes<\/a> on\u00a0chromosomes<\/a>. To talk about inheritance in terms of genes and chromosomes, you need to know the language of genetics.\u00a0The terms below serve\u00a0as\u00a0a good starting point. They are illustrated in the\u00a0figure\u00a0that follows.<\/p>\n\n- A\u00a0gene<\/a><\/strong> is the part of a chromosome<\/a> that contains the\u00a0genetic code\u00a0for a given\u00a0protein<\/a>. For example, in\u00a0pea plants, a given gene might code for flower\u00a0colour.<\/li>\n
- The position of a given gene on a chromosome is called its\u00a0locus<\/a> <\/strong>(plural, loci). A gene might be located near the center, or at one end or the other of a chromosome<\/a>.<\/li>\n
- A given gene may have different normal versions, which are called alleles<\/a><\/strong>.<\/strong> For example, in\u00a0pea plants, there is a purple-flower allele (B) and a white-flower allele (b) for the flower-colour\u00a0gene. Different\u00a0alleles account for much of the variation in the traits of organisms, including people.<\/li>\n
- In sexually reproducing organisms, each individual has two copies of each type of chromosome. Paired\u00a0chromosomes\u00a0of the same type are called\u00a0homologous<\/strong>\u00a0<\/strong>chromosomes<\/strong><\/a>. They are about the same size and shape, and they have all the same genes at the same loci.<\/li>\n<\/ul>\n
Figure 5.11.2 Chromosome, Gene, Locus, and Allele. This diagram shows how the concepts of chromosome, gene, locus, and allele are related. What is the difference between a gene and a locus? Between a gene and an allele?<\/em><\/figcaption><\/figure>\n\nGenotype<\/h2>\n<\/div>\n
When\u00a0sexual reproduction<\/a>\u00a0occurs, sex\u00a0cells\u00a0(called gametes<\/a>) unite during\u00a0fertilization<\/a>\u00a0to form a single cell called a\u00a0zygote<\/a><\/strong>. The zygote inherits two of each type of chromosome, with one chromosome of each type coming from the father, and the other coming from the mother. Because homologous chromosomes<\/a> have the same genes at the same loci, each individual also inherits two copies of each gene. The two copies may be the same allele or different\u00a0alleles<\/a>. The alleles an individual inherits for a given gene make up the individual\u2019s\u00a0genotype<\/a><\/strong>. \u00a0As shown in Table 5.11.1, an organism with two of the same allele (for example, BB<\/em>\u00a0or\u00a0bb<\/em>) is called a\u00a0homozygote<\/a><\/strong>. An organism with two different alleles (in this example,\u00a0Bb<\/em>) is called a\u00a0heterozygote<\/a><\/strong>.<\/p>\nTable 5.11.1\u00a0<\/strong><\/p>\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em><\/p>\n<\/p>\n
<\/p>\n
Phenotype<\/span><\/p>\nThe expression of an organism\u2019s genotype is referred to as its\u00a0phenotype<\/a><\/strong>, and it refers to the organism\u2019s traits, such as purple or white flowers in pea plants. As you can see from Table 5.11.1, different genotypes may produce the same phenotype. In this example, both BB<\/em>\u00a0and\u00a0Bb<\/em>\u00a0genotypes produce plants with the same phenotype, purple flowers. Why does this happen? In a\u00a0Bb<\/em>\u00a0heterozygote, only the\u00a0B<\/em>\u00a0allele is expressed, so the\u00a0b <\/em>allele doesn\u2019t influence the phenotype. In general, when only one of two alleles is expressed in the phenotype, the expressed allele is called\u00a0dominant<\/a>,<\/strong>\u00a0and the allele that isn\u2019t expressed is called\u00a0recessive<\/a>.<\/strong><\/p>\nThe terms\u00a0dominant<\/em>\u00a0and\u00a0recessive<\/em> may also be used to refer to phenotypic traits. For example, purple flower colour in pea plants is a dominant trait. It shows up in the phenotype whenever a plant inherits even one dominant allele for the trait. Similarly, white flower colour is a recessive trait. Like other recessive traits, it shows up in the phenotype only when a plant inherits two<\/em>\u00a0recessive alleles for the trait.<\/p>\n\n\n5.11 Summary<\/span><\/h1>\n<\/header>\n\n\n- Mendel’s laws\u00a0of inheritance, now expressed in terms of genes<\/a>, form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n
- A gene is the part of a chromosome<\/a> that codes for a given\u00a0protein<\/a>. The position of a gene on a chromosome is its locus<\/a>.\u00a0\u00a0A given gene may have different versions, called alleles<\/a>.\u00a0Paired chromosomes of the same type are called homologous chromosomes<\/a>. They have the same size and shape, and they have the same genes at the same loci<\/a>.<\/li>\n
- The alleles an individual inherits for a given gene make up the individual’s genotype<\/a>. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n
- The expression of an organism’s genotype is referred to as its phenotype<\/a>. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.11 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define genetics.<\/li>\n
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n
- \n\n
Figure 5.11.2 Chromosome, Gene, Locus, and Allele. This diagram shows how the concepts of chromosome, gene, locus, and allele are related. What is the difference between a gene and a locus? Between a gene and an allele?<\/em>[\/caption]\n\nGenotype<\/h2>\n<\/div>\nWhen\u00a0[pb_glossary id=\"1624\"]sexual reproduction[\/pb_glossary]\u00a0occurs, sex\u00a0cells\u00a0(called [pb_glossary id=\"1477\"]gametes[\/pb_glossary]) unite during\u00a0[pb_glossary id=\"1470\"]fertilization[\/pb_glossary]\u00a0to form a single cell called a\u00a0[pb_glossary id=\"1685\"]zygote[\/pb_glossary]<\/strong>. The zygote inherits two of each type of chromosome, with one chromosome of each type coming from the father, and the other coming from the mother. Because [pb_glossary id=\"1270\"]homologous chromosomes[\/pb_glossary] have the same genes at the same loci, each individual also inherits two copies of each gene. The two copies may be the same allele or different\u00a0[pb_glossary id=\"1190\"]alleles[\/pb_glossary]. The alleles an individual inherits for a given gene make up the individual\u2019s\u00a0[pb_glossary id=\"1485\"]genotype[\/pb_glossary]<\/strong>. \u00a0As shown in Table 5.11.1, an organism with two of the same allele (for example, BB<\/em>\u00a0or\u00a0bb<\/em>) is called a\u00a0[pb_glossary id=\"1501\"]homozygote[\/pb_glossary]<\/strong>. An organism with two different alleles (in this example,\u00a0Bb<\/em>) is called a\u00a0[pb_glossary id=\"1492\"]heterozygote[\/pb_glossary]<\/strong>.\n\nTable 5.11.1\u00a0<\/strong>\n\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em>\n\n\n\n \n\nPhenotype<\/span>\n\nThe expression of an organism\u2019s genotype is referred to as its\u00a0[pb_glossary id=\"1583\"]phenotype[\/pb_glossary]<\/strong>, and it refers to the organism\u2019s traits, such as purple or white flowers in pea plants. As you can see from Table 5.11.1, different genotypes may produce the same phenotype. In this example, both BB<\/em>\u00a0and\u00a0Bb<\/em>\u00a0genotypes produce plants with the same phenotype, purple flowers. Why does this happen? In a\u00a0Bb<\/em>\u00a0heterozygote, only the\u00a0B<\/em>\u00a0allele is expressed, so the\u00a0b <\/em>allele doesn\u2019t influence the phenotype. In general, when only one of two alleles is expressed in the phenotype, the expressed allele is called\u00a0[pb_glossary id=\"1451\"]dominant[\/pb_glossary],<\/strong>\u00a0and the allele that isn\u2019t expressed is called\u00a0[pb_glossary id=\"1605\"]recessive[\/pb_glossary].<\/strong>\n\nThe terms\u00a0dominant<\/em>\u00a0and\u00a0recessive<\/em> may also be used to refer to phenotypic traits. For example, purple flower colour in pea plants is a dominant trait. It shows up in the phenotype whenever a plant inherits even one dominant allele for the trait. Similarly, white flower colour is a recessive trait. Like other recessive traits, it shows up in the phenotype only when a plant inherits two<\/em>\u00a0recessive alleles for the trait.\n\n5.11 Summary<\/span><\/h1>\n<\/header>\n\n\n \t- Mendel's laws\u00a0of inheritance, now expressed in terms of [pb_glossary id=\"1226\"]genes[\/pb_glossary], form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n \t
- A gene is the part of a [pb_glossary id=\"1275\"]chromosome[\/pb_glossary] that codes for a given\u00a0[pb_glossary id=\"1373\"]protein[\/pb_glossary]. The position of a gene on a chromosome is its [pb_glossary id=\"1531\"]locus[\/pb_glossary].\u00a0\u00a0A given gene may have different versions, called [pb_glossary id=\"1190\"]alleles[\/pb_glossary].\u00a0Paired chromosomes of the same type are called [pb_glossary id=\"1270\"]homologous chromosomes[\/pb_glossary]. They have the same size and shape, and they have the same genes at the same [pb_glossary id=\"1531\"]loci[\/pb_glossary].<\/li>\n \t
- The alleles an individual inherits for a given gene make up the individual's [pb_glossary id=\"1485\"]genotype[\/pb_glossary]. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n \t
- The expression of an organism's genotype is referred to as its [pb_glossary id=\"1583\"]phenotype[\/pb_glossary]. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n5.11 Review Questions<\/span><\/h1>\n<\/header>\n\n\n \t- Define genetics.<\/li>\n \t
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n \t
- [h5p id=\"66\"]<\/li>\n \t
- Imagine that there are two alleles, R <\/em>and\u00a0r<\/em>, for a given gene.\u00a0R<\/em>\u00a0is dominant to\u00a0r<\/em>. Answer the following questions about this gene:\n
\n \t- What are the possible homozygous and heterozygous genotypes?<\/li>\n \t
- Which genotype or genotypes express the dominant\u00a0R\u00a0<\/em>phenotype? Explain your answer.<\/li>\n \t
- Are R <\/em>and\u00a0r<\/em>\u00a0on different loci? Why or why not?<\/li>\n \t
- Can R <\/em>and\u00a0r<\/em>\u00a0be on the same exact chromosome? Why or why not? If not, where are they located?<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<\/div>\n<\/div>\n
\n5.11 Explore More<\/span><\/h1>\n<\/header>\n\n\nhttps:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE\nAlleles and Genes, Amoeba Sisters, 2018.<\/p>\nhttps:\/\/www.youtube.com\/watch?v=OaovnS7BAoc\n
Genotypes and Phenotypes, Bozeman Science, 2011.<\/p>\n\n<\/div>\n<\/div>\n \n
Attributions<\/h2>\nFigure 5.11.1<\/strong>\n\nFather holding his baby boy with matching haircut<\/a> [photo] by Kelly Sikkema<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\n\nFigure 5.11.2<\/strong>\n\nChromosome, Gene, Locus, and Allele<\/a>\u00a0by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\n\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\n\nTable 5.11.1<\/strong>\n\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em> by Christine Miller is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\nReferences<\/h2>\n
Amoeba Sisters. (2018, February 1). Alleles and genes. YouTube. https:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE&feature=youtu.be<\/p>\n
Bozeman Science. (2011, August 4). Genotypes and phenotypes. YouTube. https:\/\/www.youtube.com\/watch?v=OaovnS7BAoc&feature=youtu.be<\/p>\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 2 Chromosome, gene, locus, and allele [digital image]. In CK-12 College Human Biology\u00a0<\/em>(Section 5.10) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-human-biology\/section\/5.9\/<\/p>\n \n\n ","rendered":"Created by: CK-12\/Adapted by Christine Miller<\/p>\nFigure 5.11.1 Like Father, Like Son.<\/em><\/figcaption><\/figure>\nLike Father, Like Son<\/h1>\n
This father-son duo share some similarities.\u00a0 The shape of their faces and their facial features look very similar. If you saw them together, you might well guess that they are father and son. People have long known that the characteristics of living things are similar between parents and their offspring. However, it wasn\u2019t until the experiments of Gregor Mendel\u00a0that scientists understood\u00a0how<\/em>\u00a0those traits are inherited.<\/p>\n\nThe Father of Genetics<\/h1>\n<\/div>\n
Mendel did experiments with pea plants to show how traits such as seed shape and flower colour are inherited. Based on his research, he developed his two well known laws of inheritance: the law of segregation<\/a> and the law of independent assortment<\/a>. When Mendel died in 1884, his work was still virtually unknown. In 1900, three other researchers working independently came to the same conclusions that Mendel had drawn almost half a century earlier. Only then was Mendel’s work rediscovered.<\/p>\nMendel knew nothing about genes, because they\u00a0were discovered after his death. He did think, however, that some type of “factors” controlled traits, and that those “factors” were passed from parents to offspring. We now call these “factors” genes.\u00a0Mendel's laws\u00a0of inheritance<\/a>, now expressed in terms of genes,\u00a0form the basis of\u00a0genetics<\/a><\/strong>, the science of heredity. For this reason, Mendel is often called the father of genetics.<\/p>\n\nThe Language of Genetics<\/h1>\n<\/div>\n
Today, we know that traits of organisms are controlled by genes<\/a> on\u00a0chromosomes<\/a>. To talk about inheritance in terms of genes and chromosomes, you need to know the language of genetics.\u00a0The terms below serve\u00a0as\u00a0a good starting point. They are illustrated in the\u00a0figure\u00a0that follows.<\/p>\n\n- A\u00a0gene<\/a><\/strong> is the part of a chromosome<\/a> that contains the\u00a0genetic code\u00a0for a given\u00a0protein<\/a>. For example, in\u00a0pea plants, a given gene might code for flower\u00a0colour.<\/li>\n
- The position of a given gene on a chromosome is called its\u00a0locus<\/a> <\/strong>(plural, loci). A gene might be located near the center, or at one end or the other of a chromosome<\/a>.<\/li>\n
- A given gene may have different normal versions, which are called alleles<\/a><\/strong>.<\/strong> For example, in\u00a0pea plants, there is a purple-flower allele (B) and a white-flower allele (b) for the flower-colour\u00a0gene. Different\u00a0alleles account for much of the variation in the traits of organisms, including people.<\/li>\n
- In sexually reproducing organisms, each individual has two copies of each type of chromosome. Paired\u00a0chromosomes\u00a0of the same type are called\u00a0homologous<\/strong>\u00a0<\/strong>chromosomes<\/strong><\/a>. They are about the same size and shape, and they have all the same genes at the same loci.<\/li>\n<\/ul>\n
Figure 5.11.2 Chromosome, Gene, Locus, and Allele. This diagram shows how the concepts of chromosome, gene, locus, and allele are related. What is the difference between a gene and a locus? Between a gene and an allele?<\/em><\/figcaption><\/figure>\n\nGenotype<\/h2>\n<\/div>\n
When\u00a0sexual reproduction<\/a>\u00a0occurs, sex\u00a0cells\u00a0(called gametes<\/a>) unite during\u00a0fertilization<\/a>\u00a0to form a single cell called a\u00a0zygote<\/a><\/strong>. The zygote inherits two of each type of chromosome, with one chromosome of each type coming from the father, and the other coming from the mother. Because homologous chromosomes<\/a> have the same genes at the same loci, each individual also inherits two copies of each gene. The two copies may be the same allele or different\u00a0alleles<\/a>. The alleles an individual inherits for a given gene make up the individual\u2019s\u00a0genotype<\/a><\/strong>. \u00a0As shown in Table 5.11.1, an organism with two of the same allele (for example, BB<\/em>\u00a0or\u00a0bb<\/em>) is called a\u00a0homozygote<\/a><\/strong>. An organism with two different alleles (in this example,\u00a0Bb<\/em>) is called a\u00a0heterozygote<\/a><\/strong>.<\/p>\nTable 5.11.1\u00a0<\/strong><\/p>\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em><\/p>\n<\/p>\n
<\/p>\n
Phenotype<\/span><\/p>\nThe expression of an organism\u2019s genotype is referred to as its\u00a0phenotype<\/a><\/strong>, and it refers to the organism\u2019s traits, such as purple or white flowers in pea plants. As you can see from Table 5.11.1, different genotypes may produce the same phenotype. In this example, both BB<\/em>\u00a0and\u00a0Bb<\/em>\u00a0genotypes produce plants with the same phenotype, purple flowers. Why does this happen? In a\u00a0Bb<\/em>\u00a0heterozygote, only the\u00a0B<\/em>\u00a0allele is expressed, so the\u00a0b <\/em>allele doesn\u2019t influence the phenotype. In general, when only one of two alleles is expressed in the phenotype, the expressed allele is called\u00a0dominant<\/a>,<\/strong>\u00a0and the allele that isn\u2019t expressed is called\u00a0recessive<\/a>.<\/strong><\/p>\nThe terms\u00a0dominant<\/em>\u00a0and\u00a0recessive<\/em> may also be used to refer to phenotypic traits. For example, purple flower colour in pea plants is a dominant trait. It shows up in the phenotype whenever a plant inherits even one dominant allele for the trait. Similarly, white flower colour is a recessive trait. Like other recessive traits, it shows up in the phenotype only when a plant inherits two<\/em>\u00a0recessive alleles for the trait.<\/p>\n\n\n5.11 Summary<\/span><\/h1>\n<\/header>\n\n\n- Mendel’s laws\u00a0of inheritance, now expressed in terms of genes<\/a>, form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n
- A gene is the part of a chromosome<\/a> that codes for a given\u00a0protein<\/a>. The position of a gene on a chromosome is its locus<\/a>.\u00a0\u00a0A given gene may have different versions, called alleles<\/a>.\u00a0Paired chromosomes of the same type are called homologous chromosomes<\/a>. They have the same size and shape, and they have the same genes at the same loci<\/a>.<\/li>\n
- The alleles an individual inherits for a given gene make up the individual’s genotype<\/a>. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n
- The expression of an organism’s genotype is referred to as its phenotype<\/a>. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.11 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define genetics.<\/li>\n
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n
- \n\n
5.11 Summary<\/span><\/h1>\n<\/header>\n\n\n \t- Mendel's laws\u00a0of inheritance, now expressed in terms of [pb_glossary id=\"1226\"]genes[\/pb_glossary], form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n \t
- A gene is the part of a [pb_glossary id=\"1275\"]chromosome[\/pb_glossary] that codes for a given\u00a0[pb_glossary id=\"1373\"]protein[\/pb_glossary]. The position of a gene on a chromosome is its [pb_glossary id=\"1531\"]locus[\/pb_glossary].\u00a0\u00a0A given gene may have different versions, called [pb_glossary id=\"1190\"]alleles[\/pb_glossary].\u00a0Paired chromosomes of the same type are called [pb_glossary id=\"1270\"]homologous chromosomes[\/pb_glossary]. They have the same size and shape, and they have the same genes at the same [pb_glossary id=\"1531\"]loci[\/pb_glossary].<\/li>\n \t
- The alleles an individual inherits for a given gene make up the individual's [pb_glossary id=\"1485\"]genotype[\/pb_glossary]. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n \t
- The expression of an organism's genotype is referred to as its [pb_glossary id=\"1583\"]phenotype[\/pb_glossary]. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n5.11 Review Questions<\/span><\/h1>\n<\/header>\n\n\n \t- Define genetics.<\/li>\n \t
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n \t
- [h5p id=\"66\"]<\/li>\n \t
- Imagine that there are two alleles, R <\/em>and\u00a0r<\/em>, for a given gene.\u00a0R<\/em>\u00a0is dominant to\u00a0r<\/em>. Answer the following questions about this gene:\n
\n \t- What are the possible homozygous and heterozygous genotypes?<\/li>\n \t
- Which genotype or genotypes express the dominant\u00a0R\u00a0<\/em>phenotype? Explain your answer.<\/li>\n \t
- Are R <\/em>and\u00a0r<\/em>\u00a0on different loci? Why or why not?<\/li>\n \t
- Can R <\/em>and\u00a0r<\/em>\u00a0be on the same exact chromosome? Why or why not? If not, where are they located?<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<\/div>\n<\/div>\n
\n5.11 Explore More<\/span><\/h1>\n<\/header>\n\n\nhttps:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE\nAlleles and Genes, Amoeba Sisters, 2018.<\/p>\nhttps:\/\/www.youtube.com\/watch?v=OaovnS7BAoc\n
Genotypes and Phenotypes, Bozeman Science, 2011.<\/p>\n\n<\/div>\n<\/div>\n \n
Attributions<\/h2>\nFigure 5.11.1<\/strong>\n\nFather holding his baby boy with matching haircut<\/a> [photo] by Kelly Sikkema<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\n\nFigure 5.11.2<\/strong>\n\nChromosome, Gene, Locus, and Allele<\/a>\u00a0by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\n\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\n\nTable 5.11.1<\/strong>\n\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em> by Christine Miller is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\nReferences<\/h2>\n
Amoeba Sisters. (2018, February 1). Alleles and genes. YouTube. https:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE&feature=youtu.be<\/p>\n
Bozeman Science. (2011, August 4). Genotypes and phenotypes. YouTube. https:\/\/www.youtube.com\/watch?v=OaovnS7BAoc&feature=youtu.be<\/p>\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 2 Chromosome, gene, locus, and allele [digital image]. In CK-12 College Human Biology\u00a0<\/em>(Section 5.10) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-human-biology\/section\/5.9\/<\/p>\n \n\n ","rendered":"Created by: CK-12\/Adapted by Christine Miller<\/p>\nFigure 5.11.1 Like Father, Like Son.<\/em><\/figcaption><\/figure>\nLike Father, Like Son<\/h1>\n
This father-son duo share some similarities.\u00a0 The shape of their faces and their facial features look very similar. If you saw them together, you might well guess that they are father and son. People have long known that the characteristics of living things are similar between parents and their offspring. However, it wasn\u2019t until the experiments of Gregor Mendel\u00a0that scientists understood\u00a0how<\/em>\u00a0those traits are inherited.<\/p>\n\nThe Father of Genetics<\/h1>\n<\/div>\n
Mendel did experiments with pea plants to show how traits such as seed shape and flower colour are inherited. Based on his research, he developed his two well known laws of inheritance: the law of segregation<\/a> and the law of independent assortment<\/a>. When Mendel died in 1884, his work was still virtually unknown. In 1900, three other researchers working independently came to the same conclusions that Mendel had drawn almost half a century earlier. Only then was Mendel’s work rediscovered.<\/p>\nMendel knew nothing about genes, because they\u00a0were discovered after his death. He did think, however, that some type of “factors” controlled traits, and that those “factors” were passed from parents to offspring. We now call these “factors” genes.\u00a0Mendel's laws\u00a0of inheritance<\/a>, now expressed in terms of genes,\u00a0form the basis of\u00a0genetics<\/a><\/strong>, the science of heredity. For this reason, Mendel is often called the father of genetics.<\/p>\n\nThe Language of Genetics<\/h1>\n<\/div>\n
Today, we know that traits of organisms are controlled by genes<\/a> on\u00a0chromosomes<\/a>. To talk about inheritance in terms of genes and chromosomes, you need to know the language of genetics.\u00a0The terms below serve\u00a0as\u00a0a good starting point. They are illustrated in the\u00a0figure\u00a0that follows.<\/p>\n\n- A\u00a0gene<\/a><\/strong> is the part of a chromosome<\/a> that contains the\u00a0genetic code\u00a0for a given\u00a0protein<\/a>. For example, in\u00a0pea plants, a given gene might code for flower\u00a0colour.<\/li>\n
- The position of a given gene on a chromosome is called its\u00a0locus<\/a> <\/strong>(plural, loci). A gene might be located near the center, or at one end or the other of a chromosome<\/a>.<\/li>\n
- A given gene may have different normal versions, which are called alleles<\/a><\/strong>.<\/strong> For example, in\u00a0pea plants, there is a purple-flower allele (B) and a white-flower allele (b) for the flower-colour\u00a0gene. Different\u00a0alleles account for much of the variation in the traits of organisms, including people.<\/li>\n
- In sexually reproducing organisms, each individual has two copies of each type of chromosome. Paired\u00a0chromosomes\u00a0of the same type are called\u00a0homologous<\/strong>\u00a0<\/strong>chromosomes<\/strong><\/a>. They are about the same size and shape, and they have all the same genes at the same loci.<\/li>\n<\/ul>\n
Figure 5.11.2 Chromosome, Gene, Locus, and Allele. This diagram shows how the concepts of chromosome, gene, locus, and allele are related. What is the difference between a gene and a locus? Between a gene and an allele?<\/em><\/figcaption><\/figure>\n\nGenotype<\/h2>\n<\/div>\n
When\u00a0sexual reproduction<\/a>\u00a0occurs, sex\u00a0cells\u00a0(called gametes<\/a>) unite during\u00a0fertilization<\/a>\u00a0to form a single cell called a\u00a0zygote<\/a><\/strong>. The zygote inherits two of each type of chromosome, with one chromosome of each type coming from the father, and the other coming from the mother. Because homologous chromosomes<\/a> have the same genes at the same loci, each individual also inherits two copies of each gene. The two copies may be the same allele or different\u00a0alleles<\/a>. The alleles an individual inherits for a given gene make up the individual\u2019s\u00a0genotype<\/a><\/strong>. \u00a0As shown in Table 5.11.1, an organism with two of the same allele (for example, BB<\/em>\u00a0or\u00a0bb<\/em>) is called a\u00a0homozygote<\/a><\/strong>. An organism with two different alleles (in this example,\u00a0Bb<\/em>) is called a\u00a0heterozygote<\/a><\/strong>.<\/p>\nTable 5.11.1\u00a0<\/strong><\/p>\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em><\/p>\n<\/p>\n
<\/p>\n
Phenotype<\/span><\/p>\nThe expression of an organism\u2019s genotype is referred to as its\u00a0phenotype<\/a><\/strong>, and it refers to the organism\u2019s traits, such as purple or white flowers in pea plants. As you can see from Table 5.11.1, different genotypes may produce the same phenotype. In this example, both BB<\/em>\u00a0and\u00a0Bb<\/em>\u00a0genotypes produce plants with the same phenotype, purple flowers. Why does this happen? In a\u00a0Bb<\/em>\u00a0heterozygote, only the\u00a0B<\/em>\u00a0allele is expressed, so the\u00a0b <\/em>allele doesn\u2019t influence the phenotype. In general, when only one of two alleles is expressed in the phenotype, the expressed allele is called\u00a0dominant<\/a>,<\/strong>\u00a0and the allele that isn\u2019t expressed is called\u00a0recessive<\/a>.<\/strong><\/p>\nThe terms\u00a0dominant<\/em>\u00a0and\u00a0recessive<\/em> may also be used to refer to phenotypic traits. For example, purple flower colour in pea plants is a dominant trait. It shows up in the phenotype whenever a plant inherits even one dominant allele for the trait. Similarly, white flower colour is a recessive trait. Like other recessive traits, it shows up in the phenotype only when a plant inherits two<\/em>\u00a0recessive alleles for the trait.<\/p>\n\n\n5.11 Summary<\/span><\/h1>\n<\/header>\n\n\n- Mendel’s laws\u00a0of inheritance, now expressed in terms of genes<\/a>, form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n
- A gene is the part of a chromosome<\/a> that codes for a given\u00a0protein<\/a>. The position of a gene on a chromosome is its locus<\/a>.\u00a0\u00a0A given gene may have different versions, called alleles<\/a>.\u00a0Paired chromosomes of the same type are called homologous chromosomes<\/a>. They have the same size and shape, and they have the same genes at the same loci<\/a>.<\/li>\n
- The alleles an individual inherits for a given gene make up the individual’s genotype<\/a>. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n
- The expression of an organism’s genotype is referred to as its phenotype<\/a>. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.11 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define genetics.<\/li>\n
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n
- \n\n
- \n \t
- Mendel's laws\u00a0of inheritance, now expressed in terms of [pb_glossary id=\"1226\"]genes[\/pb_glossary], form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n \t
- A gene is the part of a [pb_glossary id=\"1275\"]chromosome[\/pb_glossary] that codes for a given\u00a0[pb_glossary id=\"1373\"]protein[\/pb_glossary]. The position of a gene on a chromosome is its [pb_glossary id=\"1531\"]locus[\/pb_glossary].\u00a0\u00a0A given gene may have different versions, called [pb_glossary id=\"1190\"]alleles[\/pb_glossary].\u00a0Paired chromosomes of the same type are called [pb_glossary id=\"1270\"]homologous chromosomes[\/pb_glossary]. They have the same size and shape, and they have the same genes at the same [pb_glossary id=\"1531\"]loci[\/pb_glossary].<\/li>\n \t
- The alleles an individual inherits for a given gene make up the individual's [pb_glossary id=\"1485\"]genotype[\/pb_glossary]. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n \t
- The expression of an organism's genotype is referred to as its [pb_glossary id=\"1583\"]phenotype[\/pb_glossary]. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n 5.11 Review Questions<\/span><\/h1>\n<\/header>\n
\n- \n \t
- Define genetics.<\/li>\n \t
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n \t
- [h5p id=\"66\"]<\/li>\n \t
- Imagine that there are two alleles, R <\/em>and\u00a0r<\/em>, for a given gene.\u00a0R<\/em>\u00a0is dominant to\u00a0r<\/em>. Answer the following questions about this gene:\n
- \n \t
- What are the possible homozygous and heterozygous genotypes?<\/li>\n \t
- Which genotype or genotypes express the dominant\u00a0R\u00a0<\/em>phenotype? Explain your answer.<\/li>\n \t
- Are R <\/em>and\u00a0r<\/em>\u00a0on different loci? Why or why not?<\/li>\n \t
- Can R <\/em>and\u00a0r<\/em>\u00a0be on the same exact chromosome? Why or why not? If not, where are they located?<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<\/div>\n<\/div>\n
\n 5.11 Explore More<\/span><\/h1>\n<\/header>\n
\n\nhttps:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE\nAlleles and Genes, Amoeba Sisters, 2018.<\/p>\nhttps:\/\/www.youtube.com\/watch?v=OaovnS7BAoc\n
Genotypes and Phenotypes, Bozeman Science, 2011.<\/p>\n\n<\/div>\n<\/div>\n \n
Attributions<\/h2>\nFigure 5.11.1<\/strong>\n\nFather holding his baby boy with matching haircut<\/a> [photo] by Kelly Sikkema<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\n\nFigure 5.11.2<\/strong>\n\nChromosome, Gene, Locus, and Allele<\/a>\u00a0by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\n\n
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\n\nTable 5.11.1<\/strong>\n\nAllele Combinations Associated With the Terms Homozygous and Heterozygous<\/em> by Christine Miller is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\nReferences<\/h2>\n
Amoeba Sisters. (2018, February 1). Alleles and genes. YouTube. https:\/\/www.youtube.com\/watch?v=pv3Kj0UjiLE&feature=youtu.be<\/p>\n
Bozeman Science. (2011, August 4). Genotypes and phenotypes. YouTube. https:\/\/www.youtube.com\/watch?v=OaovnS7BAoc&feature=youtu.be<\/p>\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 2 Chromosome, gene, locus, and allele [digital image]. In CK-12 College Human Biology\u00a0<\/em>(Section 5.10) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-human-biology\/section\/5.9\/<\/p>\n \n\n ","rendered":"
Created by: CK-12\/Adapted by Christine Miller<\/p>\n
Figure 5.11.1 Like Father, Like Son.<\/em><\/figcaption><\/figure>\n Like Father, Like Son<\/h1>\n
This father-son duo share some similarities.\u00a0 The shape of their faces and their facial features look very similar. If you saw them together, you might well guess that they are father and son. People have long known that the characteristics of living things are similar between parents and their offspring. However, it wasn\u2019t until the experiments of Gregor Mendel\u00a0that scientists understood\u00a0how<\/em>\u00a0those traits are inherited.<\/p>\n
\nThe Father of Genetics<\/h1>\n<\/div>\n
Mendel did experiments with pea plants to show how traits such as seed shape and flower colour are inherited. Based on his research, he developed his two well known laws of inheritance: the law of segregation<\/a> and the law of independent assortment<\/a>. When Mendel died in 1884, his work was still virtually unknown. In 1900, three other researchers working independently came to the same conclusions that Mendel had drawn almost half a century earlier. Only then was Mendel’s work rediscovered.<\/p>\n
Mendel knew nothing about genes, because they\u00a0were discovered after his death. He did think, however, that some type of “factors” controlled traits, and that those “factors” were passed from parents to offspring. We now call these “factors” genes.\u00a0Mendel's laws\u00a0of inheritance<\/a>, now expressed in terms of genes,\u00a0form the basis of\u00a0genetics<\/a><\/strong>, the science of heredity. For this reason, Mendel is often called the father of genetics.<\/p>\n
\nThe Language of Genetics<\/h1>\n<\/div>\n
Today, we know that traits of organisms are controlled by genes<\/a> on\u00a0chromosomes<\/a>. To talk about inheritance in terms of genes and chromosomes, you need to know the language of genetics.\u00a0The terms below serve\u00a0as\u00a0a good starting point. They are illustrated in the\u00a0figure\u00a0that follows.<\/p>\n
- \n
- A\u00a0gene<\/a><\/strong> is the part of a chromosome<\/a> that contains the\u00a0genetic code\u00a0for a given\u00a0protein<\/a>. For example, in\u00a0pea plants, a given gene might code for flower\u00a0colour.<\/li>\n
- The position of a given gene on a chromosome is called its\u00a0locus<\/a> <\/strong>(plural, loci). A gene might be located near the center, or at one end or the other of a chromosome<\/a>.<\/li>\n
- A given gene may have different normal versions, which are called alleles<\/a><\/strong>.<\/strong> For example, in\u00a0pea plants, there is a purple-flower allele (B) and a white-flower allele (b) for the flower-colour\u00a0gene. Different\u00a0alleles account for much of the variation in the traits of organisms, including people.<\/li>\n
- In sexually reproducing organisms, each individual has two copies of each type of chromosome. Paired\u00a0chromosomes\u00a0of the same type are called\u00a0homologous<\/strong>\u00a0<\/strong>chromosomes<\/strong><\/a>. They are about the same size and shape, and they have all the same genes at the same loci.<\/li>\n<\/ul>\n
Figure 5.11.2 Chromosome, Gene, Locus, and Allele. This diagram shows how the concepts of chromosome, gene, locus, and allele are related. What is the difference between a gene and a locus? Between a gene and an allele?<\/em><\/figcaption><\/figure>\n \nGenotype<\/h2>\n<\/div>\n
When\u00a0sexual reproduction<\/a>\u00a0occurs, sex\u00a0cells\u00a0(called gametes<\/a>) unite during\u00a0fertilization<\/a>\u00a0to form a single cell called a\u00a0zygote<\/a><\/strong>. The zygote inherits two of each type of chromosome, with one chromosome of each type coming from the father, and the other coming from the mother. Because homologous chromosomes<\/a> have the same genes at the same loci, each individual also inherits two copies of each gene. The two copies may be the same allele or different\u00a0alleles<\/a>. The alleles an individual inherits for a given gene make up the individual\u2019s\u00a0genotype<\/a><\/strong>. \u00a0As shown in Table 5.11.1, an organism with two of the same allele (for example, BB<\/em>\u00a0or\u00a0bb<\/em>) is called a\u00a0homozygote<\/a><\/strong>. An organism with two different alleles (in this example,\u00a0Bb<\/em>) is called a\u00a0heterozygote<\/a><\/strong>.<\/p>\n
Table 5.11.1\u00a0<\/strong><\/p>\n
Allele Combinations Associated With the Terms Homozygous and Heterozygous<\/em><\/p>\n
<\/p>\n<\/p>\n
Phenotype<\/span><\/p>\n
The expression of an organism\u2019s genotype is referred to as its\u00a0phenotype<\/a><\/strong>, and it refers to the organism\u2019s traits, such as purple or white flowers in pea plants. As you can see from Table 5.11.1, different genotypes may produce the same phenotype. In this example, both BB<\/em>\u00a0and\u00a0Bb<\/em>\u00a0genotypes produce plants with the same phenotype, purple flowers. Why does this happen? In a\u00a0Bb<\/em>\u00a0heterozygote, only the\u00a0B<\/em>\u00a0allele is expressed, so the\u00a0b <\/em>allele doesn\u2019t influence the phenotype. In general, when only one of two alleles is expressed in the phenotype, the expressed allele is called\u00a0dominant<\/a>,<\/strong>\u00a0and the allele that isn\u2019t expressed is called\u00a0recessive<\/a>.<\/strong><\/p>\n
The terms\u00a0dominant<\/em>\u00a0and\u00a0recessive<\/em> may also be used to refer to phenotypic traits. For example, purple flower colour in pea plants is a dominant trait. It shows up in the phenotype whenever a plant inherits even one dominant allele for the trait. Similarly, white flower colour is a recessive trait. Like other recessive traits, it shows up in the phenotype only when a plant inherits two<\/em>\u00a0recessive alleles for the trait.<\/p>\n
\n\n 5.11 Summary<\/span><\/h1>\n<\/header>\n
\n- \n
- Mendel’s laws\u00a0of inheritance, now expressed in terms of genes<\/a>, form the basis of genetics, which is the science of heredity.\u00a0This is why Mendel is often called the father of genetics.<\/li>\n
- A gene is the part of a chromosome<\/a> that codes for a given\u00a0protein<\/a>. The position of a gene on a chromosome is its locus<\/a>.\u00a0\u00a0A given gene may have different versions, called alleles<\/a>.\u00a0Paired chromosomes of the same type are called homologous chromosomes<\/a>. They have the same size and shape, and they have the same genes at the same loci<\/a>.<\/li>\n
- The alleles an individual inherits for a given gene make up the individual’s genotype<\/a>. An organism with two of the same allele is called a homozygote, and an individual with two different alleles is called a heterozygote.<\/li>\n
- The expression of an organism’s genotype is referred to as its phenotype<\/a>. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n\n 5.11 Review Questions<\/span><\/h1>\n<\/header>\n
\n- \n
- Define genetics.<\/li>\n
- Why is Gregor Mendel called the father of genetics if genes were not discovered until after his death?<\/li>\n
- \n\n
- A gene is the part of a chromosome<\/a> that codes for a given\u00a0protein<\/a>. The position of a gene on a chromosome is its locus<\/a>.\u00a0\u00a0A given gene may have different versions, called alleles<\/a>.\u00a0Paired chromosomes of the same type are called homologous chromosomes<\/a>. They have the same size and shape, and they have the same genes at the same loci<\/a>.<\/li>\n
- The position of a given gene on a chromosome is called its\u00a0locus<\/a> <\/strong>(plural, loci). A gene might be located near the center, or at one end or the other of a chromosome<\/a>.<\/li>\n
- Are R <\/em>and\u00a0r<\/em>\u00a0on different loci? Why or why not?<\/li>\n \t