Question

DIHYBRID CROSSES

In all of the examples we have only been concerned with one trait. It is possible, however, to track the inheritance of more than one trait at a time. When one is investigating the inheritance of two traits at once the cross is called a dihybrid cross. Strictly speaking, a dihybrid cross is one between two individuals that are heterozygous for two traits, meaning that they are hybrids in two senses. For example, in humans eye color is determined by multiple factors, but if we compare only blue eyes to brown eyes, brown is dominant (R) and blue acts as a recessive allele (r). If a man heterozygous for both eye color and bent little finger has a child with a woman who also heterozygous for both traits, this would be a dihybrid cross. Which is/are possible genotypes for a person with bent little finger and blue eyes?
1. bbrr
2. BBRR
3. BBrr
4. Bbrr
Referring to the previous question, which is/are possible genotypes for a person with straight little finger and blue eyes?
1. bbrr
2. BbRr
3. Bbrr
4. bbRr

Answer 1

Question 1: bbrr

Question 2: bbRr

Step-by-step explanation:

To address the first question, the possible genotype for someone with bent little finger and blue eyes would be bbrr.

Since brown eye (B) is dominant over blue eyes (b), in order for the blue eye color to be expressed, it has to be in bb condition. The only option with bb genotype is option 1.

For the second question, the possible genotype for a person with a straight little finger and blue eyes would be bbRr.

Blue eye genotype is bb as explained in the first question while straight little finger would be Rr since the bent little finger has been represented by the genotype rr in the first question.