Genetic Crosses Question:
A brown coat is dominant to a white coat in cattle. A farmer has a brown bull. How would you determine whether the bull is a heterozygote for the dominant allele?
Answer (3)
You would need to look at the bull's parents to see what colors they have.
To determine if a brown bull with a dominant phenotype is a homozygote or heterozygote for that trait, one can perform a test cross. This involves mating the bull with a homozygous recessive individual (i.e., a cow with a white coat, if white is the recessive trait). If the bull is a homozygote (BB), all offspring will have brown coats. However, if the bull is a heterozygote (Bb), then statistically, there will be a 50% chance that any given offspring will have a white coat, resulting from the combination of the bull's recessive allele (b) and the cow's two recessive alleles (bb).
To determine if a brown bull is heterozygous, perform a test cross by mating it with a homozygous recessive white cow. Observe the offspring: all brown implies homozygous dominant (BB), whereas a mix of brown and white implies heterozygous (Bb). This method utilizes Mendelian genetics for clear results.
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