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BIOLOGY, Which is TRUE?

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Dencology

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What genetic information can be deduced if crossing of a male white cat with a female black cat produces 1 black and 3 white kittens while crossing of the same male cat with another black female cat results in 3 black and 1 white progenies?
I. The white allele is dominant while the black allele is recessive.
II. The white allele is recessive while the black allele is dominant.
III. Both the black parents are recessive homozygotes if the white allele is dominant.
IV. Both the black parents are heterozygotes if the white allele is recessive.
 

Sublimation

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What genetic information can be deduced if crossing of a male white cat with a female black cat produces 1 black and 3 white kittens while crossing of the same male cat with another black female cat results in 3 black and 1 white progenies?
I. The white allele is dominant while the black allele is recessive.
II. The white allele is recessive while the black allele is dominant.
III. Both the black parents are recessive homozygotes if the white allele is dominant.
IV. Both the black parents are heterozygotes if the white allele is recessive.


The answer is 4. The reason for this is if white allele was recessive then the male cat must carry both recessive genotypes. Therefore, there will always be a 50 50 chance of the offspring to be white or black. now the overall cross produces 4 white and 4 black cats. a 1:1 ratio. And you will only get that with a white recessive allele. y? well if you take choice 3. it states the white allele is dominant therefore the male cat can have the black allele, giving it the same phenotype ratio. BUT dont be fooled you can easily say that the white cat is homozygote and it will produce a offspring of all white cats. therefore due to the birth fo black cats we kno it cannot be a homozygote. the only condition that is not changed by this and will produce the offspring ratio is the 4th condition and therefore answer is 4.
 

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