BI226 Lecture Notes - Lecture 2: Lethal Allele, Hh Blood Group, Allele Frequency
Document Summary
Some phenotypic variation poses a challenge to mendelian analysis. Treasure (cid:455)our e(cid:454)(cid:272)eptio(cid:374)s the(cid:455) tell there is (cid:373)ore to (cid:272)o(cid:373)e a(cid:374)d (cid:449)here the (cid:374)e(cid:454)t (cid:272)o(cid:374)stru(cid:272)tio(cid:374) is to (cid:271)e- Crosses of pure-breeding lines can result in progeny phenotypes that don"t appear to follow. Mendel"s rules: no definitively dominant or recessive allele, more than two alleles exist, multiple genes involved, gene-environment interactions. A gene may have >2 alleles (multiple alleles0. Pleiotropy- one gene may contribute to several characteristics: recessive lethal alleles, delayed lethality. The phenotype of the heterozygote defines the dominance relationship of two alleles. Complete dominance: hybrid resembles one of the two parents. Flower color in snapdragons is an example of incomplete dominance. Crosses of pure-breeding red with pure-breeding white results in all pink f1 progeny. Pink flowers in snapdragons are the result of incomplete dominance. Molecular explanation for incomplete dominance in snapdragon flower color.
