HMB265H1 Lecture Notes - Lecture 6: Penetrance, Zygosity, Epistasis
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HMB265H1 Full Course Notes
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Mutations (chance alterations of the genetic mutation) arise spontaneously in nature and make it possible to follow gene transmission. Monomorphic: a gene with only one common, wild-type allele: e. g. , agouti gene on mice. Polymorphic: a gene with more than one common allele: e. g. , abo blood type, common variants: high-frequency allele (even though all the different alleles are considered as wild-type) Mutant alleles: rare or newly arisen alleles of any gene. Genotypic class: each class defined in terms of the presence or absence of the dominant alleles of two: dominance and recessiveness of alleles at both genes must be complete; no incomplete dominance of codominance. Complementary gene action: two genes acting on the same trait in the same pathway: one dominant allele of each of the two genotypes is necessary, e. g. , sweat pea flower colour. Allelism: mutant alleles occur at the same locus and thus cannot complement each other so the phenotype is mutant.