What is the usual phenotypic ratio in the second generation of a dihybrid cross?
Answer and explanation
Correct answer: 9:3:3:1
The governing concept is the F2 phenotypic ratio of a standard Mendelian dihybrid cross with independent assortment and complete dominance. Each parent in AaBb × AaBb can form AB, Ab, aB and ab gametes. Combining these gives four phenotype classes in the ratio 9 showing both dominant traits, 3 showing the first dominant and second recessive, 3 showing the first recessive and second dominant, and 1 showing both recessive traits. Therefore B is correct.
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What is the correct answer to this question?
9:3:3:1
Why is this the correct answer?
The governing concept is the F2 phenotypic ratio of a standard Mendelian dihybrid cross with independent assortment and complete dominance. Each parent in AaBb × AaBb can form AB, Ab, aB and ab gametes. Combining these gives four phenotype classes in the ratio 9 showing both dominant traits, 3 showing the first dominant and second recessive, 3 showing the first recessive and second dominant, and 1 showing both recessive traits. Therefore B is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: World of Living. Topic: Heredity and Evolution.
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