Name: Sex Determination (Drosophila melanogaster)
Uploaded: 2019-07-19
Duration: 7 min 20 s
Description: Drosophila melanogaster or the common fruit fly has contributed a lot to genetics. One of them is its sex determination system with more than five types of s...

Question

A breeder has several black rabbits and white rabbits. He knows that black fur in rabbits is caused by a dominant allele, B. White fur is caused by the recessive allele a. Explain what the breeder can do to determine the genotype of one of his black rabbit. Use genetic diagrams as per the answer.

Accepted Answer

An organism that shows a dominant characteristic could be either homozygous for the dominant allele or heterozygous. Example: In rabbits, the allele for black fur (B) is dominant to the allele for white fur (b). The black rabbit has the genotype BB or Bb. It can find out the genotype of an individual with the dominant phenotype for a particular gene by crossing it with one known to have the homozygous recessive genotype for the same gene. This is called test cross. Hence, it can be possible to find out the genotype of the black rabbit by crossing it with a white one.

The test cross is shown below:

If the black rabbit is heterozygous:

If the black rabbit is homozygous:

Based on the results, if any of the offspring show recessive phenotypic character (white fur), then it must mean that the black rabbit has an allele for white fur. Hence, it should be heterozygous. If none of the rabbit is white, it means that the black parent rabbit is homozygous for the black fur allele.

A breeder has several black rabbits and white rabbits. He knows that black fur in rabbits is caused by a dominant allele, B. White fur is caused by the recessive allele a. Explain what the breeder can do to determine the genotype of one of his black rabbit. Use genetic diagrams as per the answer.

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