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In genetics, underdominance, also known as homozygote advantage, heterozygote disadvantage, or negative overdominance," [1] is the opposite of overdominance. It is the selection against the heterozygote , causing disruptive selection [ 2 ] and divergent genotypes .
Autosomal dominant and autosomal recessive inheritance, the two most common Mendelian inheritance patterns. An autosome is any chromosome other than a sex chromosome.. In genetics, dominance is the phenomenon of one variant of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome.
This glossary of genetics and evolutionary biology is a list of definitions of terms and concepts used in the study of genetics and evolutionary biology, as well as sub-disciplines and related fields, with an emphasis on classical genetics, quantitative genetics, population biology, phylogenetics, speciation, and systematics.
These classifications are still widely used in Drosophila genetics to describe mutations. For a more general description of mutations, see mutation, and for a discussion of allele interactions, see dominance relationship. Key: In the following sections, alleles are referred to as +=wildtype, m=mutant, Df=gene deletion, Dp=gene duplication.
Pseudodominance is the situation in which the inheritance of a recessive trait mimics a dominant pattern. [1]Normally, two recessive alleles need to be inherited (one from each parent) for the recessive trait to be expressed but recessive merely means that the trait is only expressed in the absence of the dominant alleles.
Genetic variance has three major components: the additive genetic variance, dominance variance, and epistatic variance. [3] Additive genetic variance involves the inheritance of a particular allele from your parent and this allele's independent effect on the specific phenotype, which will cause the phenotype deviation from the mean phenotype.
Written Definitions: Each glossary entry has a written definition that has been reviewed for clarity and accuracy by teams of science educators and genetic researchers. All of the definitions were written by the same Ph.D.-level science writer for consistency and accuracy. Illustrations:
The opposite situation, where all genes show dominance in the same direction, is called directional dominance. [1] In the same example, for both genes A and B increased height is dominant. According to Broadhurst, ambidirectional dominance is the result of stabilising selection in the evolutionary past. [ 1 ]