Question

Use the following information to answer the questions below. Skin color in a certain species of fish is inherited via a single gene with four different alleles. 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

1/2 = 50% of the progeny is expected to have 5 units of color → S1S4 + S2S3

Step-by-step explanation:

Available data:

• Single gene with four different alleles → S1, S2, S3, S4
• Each allele confers a unit of color darkness
• S1 one unit
• S2 two units
• S3 three units
• S4 four units

Cross:

Parentals) S1S3 x S2S4

Gametes) S1 S3 S2 S4

F1) 1/4 = 25% of the progeny is expected to be S1S2 → 3 units

1/4 = 25% of the progeny is expected to be S1S4 → 5 units

1/4 = 25% of the progeny is expected to be S2S3 → 5 units

1/4 = 25% of the progeny is expected to be S3S4 → 7 units

1/2 = 50% of the progeny is expected to have 5 units of color → 1/4 = 25% S1S4 + 1/4 = 25% S2S3