BIO207H5 Lecture Notes - Lecture 6: Abo Blood Group System, Wild Type, Epistasis
Document Summary
Review mitosis and meiosis to help with test 2. Heterozygotes express different phenotype than either homozygote e. g. abo blood type. A and b are codominant, both dominant over o. Detected as distortions in segregation ratios caused by 1 or more missing classes of progeny. 1/3 (homozygous recessive are not considered b/c they won"t survive) Wild-type coat color is agouti (yellow + black pigments). Dominant: yellow pigment along entire hair -> yellow coat. Recessive embryonic lethal: all yellow mice are heterozygous bc homozygotes will die. Raly: highly expressed, protein essential for development, haplosufficient. Connects raly promoter to agouti => now agouti highly expressed. Sidestep natural selection with delayed age of onset e. g. huntington disease (hd), fatal neurodegenerative disorder, does not show symptoms until the late 30"s - 40"s (still have a chance to reproduce) Sex-limited traits: both sexes carry the genes, but are expressed in just one sex, due to differential influence of sex hormones e. g. testosterone.
