alleryStart learning →In the F2 of a YyRr self-cross, what proportion of offspring are expected to be wrinkled and green?
A1/16
B3/16
C1/4
D9/16
Answer & Solution
Correct answer: A. 1/16
1. Wrinkled seeds need the genotype rr, and green seeds need the genotype yy.
2. Considering seed texture alone, a heterozygote cross gives 1/4 rr.
3. Considering seed colour alone, the same cross gives 1/4 yy.
4. The sorting of texture alleles and colour alleles are independent events, so apply the product rule.
5. Multiply: 1/4 times 1/4 equals 1/16.
6. Checking against the square, only one of the sixteen boxes reads yyrr, which agrees.
7. The value 3/16 belongs to the two mixed classes and 9/16 to the double dominant class.
8. A value of 1/4 would be the answer for a single gene, not for two together.
_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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