Pigment in mouse fur is only produced when the C allele is present. Individuals
ID: 193966 • Letter: P
Question
Pigment in mouse fur is only produced when the C allele is present. Individuals of the cc genotype are white. If color is present, it may be determined by the A, a alleles. AA or Aa results in agouti color, while aa results in black coats.
a. What F1 and F2 genotypic and phenotypic ratios are obtained from a cross between AACC and aacc mice?
b. In two testcrosses between agouti females, whose genotypes were unknown, and males of the aacc genotype, the following phenotypic ratios were obtained.
What are the genotypes of these female parents?
i. 9 agouti : 10 black
ii. 4 agouti : 5 black : 10 white
Explanation / Answer
a.
Coat colour in mice follows recessive epistatic inheritance pattern
Allele A is hypostatic to recessive allele c.
Parental cross: AACC (Agouti) X aacc (Albino)
F1 = AaCc (all agouti)
F1 selfing = AaCc X AaCc
F2:
A_C_ = Agouti = 9/16
A_cc = Albino = 3/16
aaC_ = Black = 3/16
aacc = Albino = 1/16
b.
i.
Obsreved ratio = 9 agouti : 10 black = 1:1
Test cross involves a recessive parent = aacc
Cross = AaCC X aacc
Gametes = AC aC X ac
Progeny = AaCc aaCc
ii.
Obserevd ratio = 4 agouti : 5 black : 10 white = 1:1:2
Cross = AaCc X aacc
Gametes = AC Ac aC ac X ac
Progeny:
AaCc = Agouti = 1/4
Aacc = Albino = 1/4
aaCc = Black = 1/4
aacc = ALbino = 1/4