Question

One fish of this type has alleles 1 and 3 (S1S3) and its mate has alleles 2 and 4 (S2S4). If each allele confers a unit of color darkness such that S1 has one unit, S2 has two units, and so on, then what proportion of their offspring would be expected to have five units of color?

Answer 1

Answer:

The options to the question are:

A) 1/4

B) 1/5

C) 1/8

D) 1/2

E) 0

The answer is D (1/2)

Explanation:

If each fish can possess only two allele types, a cross between a fish with allele types S1S3 and S2S4 will produce four possible offsprings using a punnet square.

S1S3 will produce S1 and S3 gametes while S2S4 will produce S2 and S4 gametes.

Each allele type confers a particular number of unit color to the fish i.e. S1 confers one unit color, S2 confers two, S3 confers 3, S4 confers 4 and so on........

A cross between S1S3 and S2S4 will yield offsprings S1S2, S1S4, S2S3 and S3S4. Combining these allele types, we will realize that only S1S4 and S2S3 will produce fishes with 5 units respectively. Hence, the probability of producing offsprings with five units of color is 2/4 or 1/2.