Answer:
C. Bb
General Formulas and Concepts:
Genetic I
Punnett Squares
Alleles
Mendelian Genetics
Explanation:
We are given that the allele B (black-haired coat) is dominant over the allele b (red-haired coat). That means it is a complete dominance and we do not have to worry about incomplete or co-dominance.
We know from Mendelian genetics that if there is a dominant allele present, then the genotype has to include the dominant allele, in this case B. The phenotype must also match the dominant allele, in this case a black-haired coat.
We are given a calf with a black-haired coat. This is the phenotype for the dominant allele B. Therefore we can eliminate answer choices B and D since they are both recessive alleles. We are left with answer choices A and C.
Since alleles come from parents, you will receive 1 allele from each parent (think about cell division and gamete production). So, if you are an offspring, you will have 2 parents and therefore 2 alleles. Therefore, C is the correct answer.
