| Autosomal Dominant |
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Information AboutAutosomal Dominant |
| CATEGORIES ABOUT DOMINANCE RELATIONSHIP | |
| classical genetics | |
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In Genetics , a dominance relationship refers to how the Allele s for a Locus interact to produce a Phenotype . There are three main kinds of dominance relationships:
In general terms, a gene contributes to production or expression of some trait or character (a ''', a locus might be in a Noncoding DNA sequence. An allele (or allelic variant) is any of the versions of some genetic locus that might exist in a Population . Regarding the iris example, there exists an allele of the locus called EYCL3 which causes the eye to be some shade of brown from lots of Eumelanin s, and another that causes few eumelanin to be produced, resulting in an iris that is blue, gray or green. Since you are Diploid , you have two copies of the locus, one inherited from your father and the other from your mother. Thus, you can be Homozygous in that locus - having one of the two allelic variants twice - or Heterozygous , with one copy of each variant. Brown eye color is the dominant trait in the iris example, whereas non-brown eye color is the '''recessive''' trait; often, non-brown is called simply "blue" due to the rarity of green and grey eyes, but this is technically incorrect (see next paragraph). If one or both of your EYCL3 loci carry the allele for the dominant trait, this trait - brown eyes - will be expressed. The "brown eyes" allele induces copious eumelanin production in the iris, whereas the "non-brown" allele causes the production of only small amounts of eumelanins. Therefore, the recessive trait in this example is simply overwhelmed by the dominant trait. To have green, blue or grey eyes, both copies of the EYCL3 locus must carry the recessive allele, to prevent strong eumelanin production in the iris. In these cases, your ultimate eye color depends on the alleles present at 2 other loci, EYCL1 and EYCL2. Green eyes are dominant over blue eyes, and these alleles are carried at the EYCL1 locus. Here, the effects, whereas the dominant vs recessiveness of a trait is due to how specific Biochemical reactions are affected by the different alleles. Note that it is phenes and phenotypes that are dominant and recessive, not the alleles or genes. Note also that the term "dominant/recessive allele", while technically incorrect, is correct as regards the allele - locus/gene relationship in dominant-recessive inheritance. "Dominant/recessive gene" is utterly wrong in most of the (Mendelian) contexts it is usually encountered; for a gene to dominate over another in expression of a phenotype, Epistatic or other forms of multi-gene expressions are required. __TOC__ NOMENCLATURE Loci are indicated in shorthand by a combination of one or a few letters - for example, in Cat Coat Genetics the alleles Mc and mc (for "mackerel tabby") play a prominent role. Alleles producing dominant traits are denoted by initial Capital Letter s; those that confer recessive traits are written with Lowercase letters. The alleles present in a locus are usually separated by a slash; in the Mc - mc case, the dominant trait is the "mackerel-stripe" pattern, and the recessive one the "classic" or "oyster" tabby pattern, and thus a classical-pattern tabby cat would carry the alleles mc/mc, whereas a mackerel-stripe tabby would be either Mc/mc or Mc/Mc. | ||
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