10. In a population of dogs, fur color is controlled by two alleles: black (B) and tan (b). The black allele shows complete dominance. If a dog has a tan fur phenotype, what is its genotype?
Answer: C
A dog with a tan fur phenotype has the genotype bb.
In a population of dogs where fur color is controlled by alleles black (B) and tan (b), the black allele is completely dominant over the tan allele. Therefore, a dog exhibiting a tan fur phenotype must possess two copies of the recessive tan allele, resulting in the genotype bb.
A) BB
The genotype BB would produce a dog with a black fur phenotype, as the presence of two dominant alleles would mask any recessive traits. Therefore, this option cannot represent a dog with a tan fur phenotype.
B) Bb
The genotype Bb would also result in a black fur phenotype because the dominant black allele (B) would mask the effect of the recessive tan allele (b). Consequently, this option is incorrect for a dog exhibiting tan fur.
C) bb
This is the correct option, as a dog with the genotype bb has two copies of the recessive allele for tan fur. Since tan is a recessive trait, only dogs with this genotype will display the tan fur phenotype.
D) Not enough information
This option is not valid in this context, as the question provides sufficient information about the dominance relationship between the alleles and the fur color phenotype. Thus, we can definitively conclude the genotype of a tan-furred dog.
Conclusion
The correct answer, bb, is the only possible genotype for a dog with a tan fur phenotype, as both alleles must be recessive for the trait to be expressed. All other options either represent dominant traits or misinterpret the information provided, confirming that bb is the definitive and accurate choice.