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Peas in pods

Dominance in genetics is a relationship between alleles of one gene, in which the effect on phenotype of one allele masks the contribution of a second allele at the same locus.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The first allele is dominant and the second allele is recessive. For genes on an autosome (any chromosome other than a sex chromosome), the alleles and their associated traits are autosomal dominant or autosomal recessive. Dominance is a key concept in Mendelian inheritance and classical genetics. Often the dominant allele codes for a functional protein whereas the recessive allele does not.

A classic example of dominance is the inheritance of seed shape, for example a pea shape in peas. Peas may be round, associated with allele R or wrinkled, associated with allele r. In this case, three combinations of alleles (genotypes) are possible: RR, Rr, and rr. The RR individuals have round peas and the rr individuals have wrinkled peas. In Rr individuals the R allele masks the presence of the r allele, so these individuals also have round peas. Thus, allele R is dominant to allele r, and allele r is recessive to allele R. This use of upper case letters for dominant alleles and lower case ones for recessive alleles is a widely followed convention.

More generally, where a gene exists in two allelic versions (designated A and a), three combinations of alleles are possible: AA, Aa, and aa. If AA and aa individuals (homozygotes) show different forms of some trait (phenotypes), and Aa individuals (heterozygotes) show the same phenotype as AA individuals, then allele A is said to dominate or be dominant to or show dominance to allele a, and a is said to be recessive to A.

Dominance is not inherent to an allele. It is a relationship between alleles; one allele can be dominant over a second allele, recessive to a third allele, and codominant to a fourth. Also, an allele may be dominant for a particular aspect of phenotype but not for other aspects influenced by the same gene. Dominance differs from epistasis, a relationship in which an allele of one gene affects the expression of another allele at a different gene.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>


Dominance (genetics) sections
Intro  Background  Dominance  Nomenclature  Relationship to other genetic concepts  Molecular mechanisms  Dominant and recessive genetic diseases in humans  See also  References  External links  

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Peas in pods

Dominance in genetics is a relationship between alleles of one gene, in which the effect on phenotype of one allele masks the contribution of a second allele at the same locus.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The first allele is dominant and the second allele is recessive. For genes on an autosome (any chromosome other than a sex chromosome), the alleles and their associated traits are autosomal dominant or autosomal recessive. Dominance is a key concept in Mendelian inheritance and classical genetics. Often the dominant allele codes for a functional protein whereas the recessive allele does not.

A classic example of dominance is the inheritance of seed shape, for example a pea shape in peas. Peas may be round, associated with allele R or wrinkled, associated with allele r. In this case, three combinations of alleles (genotypes) are possible: RR, Rr, and rr. The RR individuals have round peas and the rr individuals have wrinkled peas. In Rr individuals the R allele masks the presence of the r allele, so these individuals also have round peas. Thus, allele R is dominant to allele r, and allele r is recessive to allele R. This use of upper case letters for dominant alleles and lower case ones for recessive alleles is a widely followed convention.

More generally, where a gene exists in two allelic versions (designated A and a), three combinations of alleles are possible: AA, Aa, and aa. If AA and aa individuals (homozygotes) show different forms of some trait (phenotypes), and Aa individuals (heterozygotes) show the same phenotype as AA individuals, then allele A is said to dominate or be dominant to or show dominance to allele a, and a is said to be recessive to A.

Dominance is not inherent to an allele. It is a relationship between alleles; one allele can be dominant over a second allele, recessive to a third allele, and codominant to a fourth. Also, an allele may be dominant for a particular aspect of phenotype but not for other aspects influenced by the same gene. Dominance differs from epistasis, a relationship in which an allele of one gene affects the expression of another allele at a different gene.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>


Dominance (genetics) sections
Intro  Background  Dominance  Nomenclature  Relationship to other genetic concepts  Molecular mechanisms  Dominant and recessive genetic diseases in humans  See also  References  External links  

PREVIOUS: IntroNEXT: Background
<<>>