(Problem 35a) E. W. Lindstrom crossed two corn plants with green seedlings and o
ID: 90605 • Letter: #
Question
(Problem 35a) E. W. Lindstrom crossed two corn plants with green seedlings and obtained the following progeny: 3583 green seedlings, 853 virescent-white seedlings, and 260 yellow seedlings (E. W. Lindstrom. 1921. Genetics 6:91–110). Give the genotypes for the green, virescent-white, and yellow progeny. Use A and a and B and b to denote dominant and recessive alleles for the genes involved.
Please explain why, thanks in advance.
A. green - A_B_ and A_bb, virescent-white - aaB_, yellow - aabb
B. green – AAB_, virescent-white – aaBB, yellow - aabb
C. green - AbBb, virescent-white – aaBB, yellow - aabb
D. green - AABB, virescent-white – AaBb, yellow - aabb E. green - A_B_ and A_bb, virescent-white – aaBB, yellow - aaBb
Explanation / Answer
Answer:
A. green - A_B_ and A_bb, virescent-white - aaB_, yellow - aabb
Explanation:
The given ratio seems to be 12:3:1. This ratio appears in dominant epistasis. When dominant allele ‘A’ masks the expression of allele ‘B’, the allele ‘A’ is epistatic over ‘B’. The allele ‘A’ can express itself only in the presence of ‘B’ or b allele. Therefore it is called dominant epistasis. B expresses only when ‘aa’ is present. Therefore, in 9: 3: 3: 1 ratio both 9 and 3 are expressing the ‘A’ gene the ratio is now 12: 3: 1.
AaBb(green) x AaBb(green)
AB
Ab
aB
ab
AB
AABB (Green)
AABb (Green)
AaBB (Green)
AaBb (Green)
Ab
AABb (Green)
AAbb (Green)
AaBb (Green)
Aabb (Green)
aB
AaBB (Green)
AaBb (Green)
aaBB (virescent-white )
aaBb (virescent-white )
ab
AaBb (Green)
Aabb (Green)
aaBb (virescent-white )
aabb (yellow)
AB
Ab
aB
ab
AB
AABB (Green)
AABb (Green)
AaBB (Green)
AaBb (Green)
Ab
AABb (Green)
AAbb (Green)
AaBb (Green)
Aabb (Green)
aB
AaBB (Green)
AaBb (Green)
aaBB (virescent-white )
aaBb (virescent-white )
ab
AaBb (Green)
Aabb (Green)
aaBb (virescent-white )
aabb (yellow)
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