30. Hair pigmentation in mammals follows the generic enzymatic pathway depicted
ID: 208625 • Letter: 3
Question
30. Hair pigmentation in mammals follows the generic enzymatic pathway depicted below. Enzyme A synthesizes a black pigment from a precursor, and the contribution of enzyme B results in the final agouti pigment: ent Agouti pigment Each enzyme is coded by a single allele with complete dominance. If a crossing design begins with true breeding parents for coat color with the genotypes AAbb and aaBB. What will be the expected F2 genotypic and phenotypic ratios of the eventual F2 progeny? 31. Black hair in rabbits is determined by a dominant allele, B. White hair results when a rabbit is homozygous for the recessive allele, b. Two heterozygote rabbits mate and produce a litter of three offspring. What is the probability that the offspring are born in the order white-black-white? What is the probability that the offspring are born in either the order white-black-white or black-white-black? a. b. 32. The Hopi, Zuni, and other Southwest American Indians have a relatively high frequency of albinism resulting from homozygosity for a recessive allele, a. A normally pigmented man and oman, each of who has an albino parent, bave two children a. What is the probability that both children are albino? b. What is the probability that at least one of the children is albino?Explanation / Answer
Answer:
30).
AAbb(black) x aaBB(colorless)----Parents
AaBb(agouti) -------------------F1
AaBb x AaBb-----------------------F1 x F1
AB
Ab
aB
ab
AB
AABB (Agouti)
AABb (Agouti)
AaBB (Agouti)
AaBb (Agouti)
Ab
AABb (Agouti)
AAbb (black)
AaBb (Agouti)
Aabb (black)
aB
AaBB (Agouti)
AaBb (Agouti)
aaBB (colorless)
aaBb (colorless)
ab
AaBb (Agouti)
Aabb (black)
aaBb (colorless)
aabb (colorless)
F2 phenotypic ratio:
Agouti : Black : Colorless = 9:3:4
Genotypic ratio:
1: 2: 1: 2: 4: 2: 1: 2: 1
31).
Bb x Bb
B
b
B
BB (black)
Bb (black)
b
Bb (black)
bb (white)
Balck = ¾
White = ¼
a). Probability of White-Balck-White probability = 1/4 * ¾ * ¼ =3/64
b)
Probability of black-white-black = ¾ * ¼ * ¾ = 9/64
Probability of White-Balck-White or black-white-black = 3/64 + 9/64 = 12/64= 3/16
32).
The information explains that the both man and woman are heterozygous.
Aa X Aa---Parents
A
a
A
AA (normal)
Aa (normal)
a
Aa (normal)
aa (albino)
Normal = ¾
Albino = ¼
a). Probability of both children are albino = ¼ * ¼ = 1/16
b). Probability that at least one of children is albino = ¾ * ¼ = 3/16
AB
Ab
aB
ab
AB
AABB (Agouti)
AABb (Agouti)
AaBB (Agouti)
AaBb (Agouti)
Ab
AABb (Agouti)
AAbb (black)
AaBb (Agouti)
Aabb (black)
aB
AaBB (Agouti)
AaBb (Agouti)
aaBB (colorless)
aaBb (colorless)
ab
AaBb (Agouti)
Aabb (black)
aaBb (colorless)
aabb (colorless)
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