Question

9. Examine the following crosses among Erminette chickens and the resulting feather colors of the offspring and decide what type of inheritance is involved. Then, indicate the genotypes of the parents and offspring involved in each of the crosses in the blanks provided Parents Offspring Pod Length Parent 1 Parent 2 Gray Gray 4 Black Gray 4 White Black Black all Black White White all White Black Gray % Black y Gray White | Gray - White 12 Gray Black White all Gray Pattern of inheritance for Erminette chicken feather color: Explain your answer:

Answer 1

the pattern of inheritance is Incomplete dominance.

let the alleles be B- black, W- white.

then let`s do the crosses and check the proportion of progenies.

BB- Black, WW- white, BW- Gray

1) Gray * gray

BW * BW

	B	W
B	BB ( black)	BW ( gray)
W	BW ( gray)	WW ( white)

expected proportion is black= number of black/total number=1/4

the expected proportion of Gray= number of Gray/total number=2/4=1/2

expected proportion of white= number of white/total number=1/4

2) Black * black

BB * BB

BB ( F1)

all the F1 progenies are black.

3) WW * WW

WW ( F1)

all the F1 progenies are white.

4) Black * gray

BB * BW

	B	W
B	BB ( black)	BW ( gray)

expected proportion is black= number of black/total number=1/2

the expected proportion of Gray= number of Gray/total number=1/2

5) white * gray

WW * BW

	B	W
W	BW ( Gray)	WW ( white)

  expected proportion is white= number of white/total number=1/2

the expected proportion of Gray= number of Gray/total number=1/2

6) Black * white

BB * WW

BW

all the F1 progenies are Gray

expected proportions in all crosses are same as the observed proportions so the pattern of inheritance is incomplete dominance and one gene controls the phenotype, the gene has 2 alleles.