Question

Assuming independent assortment of alleles, the expected phenotypic ratio from a dihybrid cross is

• A. 1: 1: 1: 1
• B. 4: 0: 4: 0
• C. 9: 3: 3: 1
• D. 9: 3: 4
• E. 4: 2: 8: 2

Answer 1

Answer: (C)

9: 3: 3: 1

The cross can be seen as shown in the figure.

Dihybrid cross is a cross involving two pairs of contrasting characters. When a cross is made between yellow-round and wrinkled green seeds (both pure line homozygous), plants with only yellow round seeds are F1 generation but in F2 generation, four types of combinations are observed.

Two of these combinations are similar to the parental combination and other two new combinations which are round green and wrinkled yellow. The ratio of four combinations in F2 generation comes out to be:

9 (round yellow) : 3 (round green) : 3 (wrinkled yellow) : 1 (wrinkled green)

This is called phenotypic dihybrid ratio.

So, the correct answer is '9: 3: 3: 1'.