420 The white Leghorn breed of chickens is homozygous for th

4.20 The white Leghorn breed of chickens is homozygous for the dominant allele C, which produces colored feathers. However, this breed is also homozygous for the dominant allele I of an independently assorting gene that inhibits col- oration of the feathers. Consequently, Leghorn chickens have white feathers. The white Wyandotte breed of chick- ens has neither the allele for color nor the inhibitor of color; it is therefore genotypically cc ii. What are the F2 phenotypes and proportions expected from intercrossing the progeny of a white Leghorn hen and a white Wyandotte rooster?

Solution

color dominant gene.............C inhibitor gene...................I White Leghorn hen................CCII White Wyandottes.................ccii CCII x   ccii--------------> CcIi Due to the presence of dominant inhibitor \"I\" in the offsprings genotype, the offsprings all have been white. Due to selfing of F1 offsprings............CcIi x CcIi gametes are.............CI,Ci,cI,ci results in..............9:3:3:1 ratio of White:Dark:White:White Out of the total progeny, 13/16 white and 3/16 are dark 1/4 x 3/4--------------> 3/16 (probability of ii....1/4 and probability of C_........3/4) CI Ci cI ci CI CCII (White) CCIi (White) CcII (White) CcIi(White) Ci CCIi (White) CCii (coloured) CcIi (White) Ccii (coloured) cI CcII (White) CcIi (White) ccII (White) ccIi (White) ci CcIi (White) Ccii (coloured) ccIi (White) ccii(White)