HMB265H1 Lecture Notes - Lecture 5: Consanguinity, Gamete, Penetrance

• School: UTSG
• Department: Human Biology
• Course: HMB265H1
• Professor: Maria Papaconstantinou

Document Summary

Lecture 5 mendelian genetics i: dominance, co-dominance, penetrance, expressivity. Incomplete dominance and codominance: multiple alleles, pleiotropy, variable expressivity, environmental influence. Consider: different alleles at the same locus will likely have different levels of effect on the trait. Problem: variable levels in allele activity will somehow be manifest at the phenotypic level. Dominance is not always complete: crosses between true-breeding strains can produce hybrids with phenotypes different from both parents. In a cross between two-breeding parents that differ at only one trait, the phenotype of the f1 heterozygote defines the dominance relationship between two alleles of a single gene (for complete dominance) These crosses can also produce hybrids with phenotypes that differ from the parents (incomplete dominance) F1 hybrids express an intermediate novel phenotype: neither allele is dominant or recessive to the other. Phenotypic and genotypic ratios are the same: with codominance, these crosses produce hybrids with phenotypes of both parents in an equal manner.