MCB 10 Lecture Notes - Lecture 5: Hearing Loss, Heteroplasmy, Myopathy
25 Sep 2016
School
Department
Course
Professor
Document Summary
Lethal alleles: a lethal genotype causes death before the individual can reproduce. This removes an expected progeny class following a specific cross: a double dose of a dominant allele may be lethal. Ex: pku gene has hundreds of alleles resulting in four basic phenotypes. Incomplete dominance the heterozygous phenotype is between those of homozygotes. The abo gene encodes a cell surface protein: alleles ia and ib are codominant, and both. Ib allele produces b antigen i (io) allele does not produce antigens: epistasis the phenomenon where one gene affects the are completely dominant to i expression of a second gene. Pleiotropy the phenomenon where one gene controls several functions or has more than one effect. Ex: porphyria variegata affected several members of european royal families, including king george iii. The varied illnesses and quirks appeared to be different unrelated disorders: genetic heterogeneity different genes produce identical phenotypes. Ex: hearing loss 132 autosomal recessive forms.
