dihybrid crosses - (Apr/26/2008 )

In guinea pigs, black coat colour is dominant to albino. Rough coat is dominant to smooth coat. A black smooth guinea pig was mated with an albino rough guinea pig. Their offspring were black rough and black smooth. If these were the only offspring produced over a period of years in a number of matings, what was the probable genotype of each parent?

B-black
b- albino
R- rouch
r- smooth

the answer : BbRr crossed with bbrr ??

not to sure , can someone help me .

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this is from your other post, but since you tried...

black smooth is phenotype dominant black, recessive smooth

albino rough is phenotype recessive albino, dominant rough

dominant phenotype can be homo or heterozygous

recessive phenotype must be homozygous

so, albino and smooth must be homozygous

black and rough can be either.

since all progeny are black, then the black parent must be homozygous (if heterozygous then half of the progeny would be albino)

since some of the progeny are rough and some smooth then the parent must be heterozygous dominant.

finally, the black smooth parent is BBrr and the albino rough parent is bbRr.

did you follow the reasoning? if so, then you should have no problem with the rest.

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