Two pure breeding lines of Klingon mice which differ in head type and fang lengt

Question

Two pure breeding lines of Klingon mice which differ in head type and fang length are crossed to produce F1 offspring. F1 individuals are crossed to produce F2 offspring. The F2 offspring consist of 180 bumpy head, long fang : 61 bumpy head, short fang : 59 smooth head, long fang : 20 smooth head, short fang individuals. A reciprocal cross of F1 individuals gave about the same results.

A) The recessive phenotypes are a) smooth head and short fang b) bumpy head and short fang c) bumpy head and long fang d) smooth head and long fang.

B) The number of different genotypes among the bumpy short F2 individuals is a) 1 b) 8 c) 6 d) 4 e) 2.

C) The genes affecting these two traits assort independently a) True b) False

D) A pure breeding line could contain which of the following genotypes a) Aa b) AA c) AA & Aa d) AA, Aa & aa

Explanation / Answer

Answer:

A). a) smooth head and short fang

Explanation:

80 bumpy head, long fang (A_B_): 61 bumpy head, short fang (A_bb) : 59 smooth head, long fang(aaB_) : 20 smooth head, short fang (aabb) individuals. = 9:3:3:1

During F2 generation of Dihybrid cross, 1/16 of progeny are double recessive phenotypes. So the double recessive phenotypes are a) smooth head and short fang.

B). 2

Explanation:

Actually, 3/16 of bumpy head and long fangs are produced. It means three different genotypes. But in the option with number three is not given

C). a. True

D). b. AA

Explanation: True breeding means that they have same alleles of genotype, AA or aa

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