HMB265H1 Lecture Notes - Lecture 5: Hemoglobin, Porphyrin, Porphyria

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

Document Summary

Hmb265: human and general genetics lecture #5. Wrinkles on mendel"s laws: incomplete dominance and codominance, multiple alleles, pleiotropy, variable expressivity, incomplete penetrance, environmental influence. Reading: hartwell et al. , 1st can. edition, chapter 2 (emphasis on pages 33-42 and pages. Different alleles at the same locus will likely have different levels of effect on the trait. Variable levels in allele activity will somehow be manifest at the phenotypic level. Crosses between true-breeding strains can produce hybrids with phenotypes different from both parents. Incomplete dominance: f1 hybrids that differ from both parents express an intermediate phenotype. Neither allele is dominant nor recessive to the other: phenotypic ratios are same as genotypic ratios. Codominance: f1 hybrids express the phenotype of both parents equally, phenotypic ratios are same as genotypic ratios. Each genotype has a specific phenotype: i. e. pink. Example: familial hypercholesteraemia: extra production of cholesterol, results in fatty substance deposits. The heterozygous phenotype is distinct from either homozygous phenotype - an intermediate phenotype.