Multiple choice

The normal phenotypic ratio of dihybrid cross is

  1. 9: 3: 3: 1

  2. 3: 1

  3. 12: 3: 1

  4. 9: 3: 4
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A Correct answer
Explanation

The normal phenotypic ratio for a dihybrid cross (two traits, both heterozygous parents) is 9:3:3:1. This represents 9 dominant for both traits : 3 dominant for first trait only : 3 dominant for second trait only : 1 recessive for both traits. 3:1 is the monohybrid ratio, and 9:3:4 and 12:3:1 are modified ratios seen with epistasis or lethal genes.

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