alleryStart learning →Yellow is dominant to green and round to wrinkled. What phenotypic ratio does a self-crossed YyRr plant give?
A1 to 1 to 1 to 1
B9 to 3 to 3 to 1
C3 to 3 to 1 to 1
D12 to 3 to 1 flat
Answer & Solution
Correct answer: B. 9 to 3 to 3 to 1
1. Each gene alone gives 3 dominant to 1 recessive, so the chance of the dominant phenotype is 3/4 and of the recessive is 1/4.
2. The genes assort independently, so multiply the separate chances.
3. Round and yellow is 3/4 times 3/4, which is 9/16.
4. Round and green is 3/4 times 1/4, which is 3/16, and wrinkled and yellow is also 3/16.
5. Wrinkled and green is 1/4 times 1/4, which is 1/16.
6. Multiplying every fraction by 16 gives 9 to 3 to 3 to 1.
7. That matches counting the sixteen boxes of the square directly.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 12 "Mendel's Experiments and Heredity", section 12.3 Laws of Inheritance_
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