LIFE SCIENCE

OBJECTIVE LIFE SCIENCE

GENETICS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
In guinea pigs, the allele for rough coat (R) is dominant to the allele for smooth coat (r). A rough coat male and a smooth coat female mate. They produce several offspring-50% are rough coat and 50% are smooth coat. What are the genotypes of the parents?
A
RR x rr
B
RR x Rr
C
Rr x rr
D
Rr x Rr
Explanation: 

Detailed explanation-1: -In guinea pigs, the allele for a rough coat (R) is dominant over the allele for a smooth coat (r). A heterozygous guinea pig (Rr) and homozygous recessive guinea pig (rr) have a total of nine offspring. The Punnett square for this cross shows a 50 percent chance that any particular offspring will have a smooth coat.

Detailed explanation-2: -In guinea pigs, the allele for black coat color (B) is dominant over the allele for white coat color (b). In an ideal mouse population exhibiting Hardy-Weinberg equilibrium of 31 guinea pigs, 2 are homozygous dominant, 11 are heterozygous, and 18 are homozygous recessive.

Detailed explanation-3: -Short hair is dominant which means it can express in both heterozygous(Hh) and homozygous condition(HH). If all the progeny have short hair, then the parents should have been either: HH x HH OR HH x Hh OR HH x hh.

Detailed explanation-4: -So the F1 generation formed is of genotype BbRr and the organism formed is a black rough guinea pig. In the F2 generation, 9 black rough guinea pigs, 3 smooth black guinea pigs, 3 smooth white guinea pigs, and one white smooth guinea pig are obtained.

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