Question

Brown eye color dominates the blue and is determined by an autosomal gene. Polydactyly is determined by a dominant autosomal gene. From the marriage of brown-eyed parents with polydactyly was born a child with blue eyes and a normal hand. What offspring can you expect from this marriage? What is the probability of birth of brown-eyed children with a normal hand?

Answer 1

Answer:

According to the third law of Mendel, in dihybrid crosses the inheritance of both characters is carried out independently of each other, and in the offspring of digeterozygotes phenotypic splitting is observed in the proportion of 9: 3: 3: 1 (9 A * B *, 3 aaB *, 3 A * bb, 1 aabb, where * in this case means that the gene can be either in a dominant or in a recessive state).

Answer on the first and second question:

9 (Brown eyes, polydactyly) : 3 (Brown eyes, normal hand) : 3 (Blue eyes, polydactyly) : 1 (Blue eyes, normal hand)

Answer 2

In this case, we can assume that brown eye color (B) is dominant over blue eye color (b), and polydactyly (P) is dominant over a normal hand (p).

Let's analyze the genotypes of the parents first:

Parent 1 (brown-eyed with polydactyly): BBPP (brown eyes, polydactyly) Parent 2 (brown-eyed with polydactyly): BBPP (brown eyes, polydactyly)

The child's phenotype is blue eyes (bb) and a normal hand (pp). From this, we can infer the child's genotype:

Child (blue eyes with a normal hand): bbpp

Now, let's determine the possible genotypes and phenotypes of the offspring from this marriage.

Possible genotypes of the offspring:

• 25% chance of BBpp (brown eyes, normal hand)
• 25% chance of bbPp (blue eyes, polydactyly)
• 25% chance of bbpp (blue eyes, normal hand)
• 25% chance of BBPp (brown eyes, polydactyly)

Possible phenotypes of the offspring:

• 25% chance of brown eyes with a normal hand
• 25% chance of blue eyes with polydactyly
• 25% chance of blue eyes with a normal hand
• 25% chance of brown eyes with polydactyly

Therefore, the probability of the birth of brown-eyed children with a normal hand is 25% or 1/4.