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Biology
Principles of Inheritance and Variation
198 questions from 38 papers, each with its answer.
- 198 questions
- 38 papers
- 5.62% of Biology
Dihybrid cross
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In Mendel's experiments with garden pea, round seed shape (RR) was dominant over wrinkled seeds (rr), yellow cotyledon (YY) was dominant over green cotyledon (yy). What are the expected phenotypes in the $F_2$ generation of the cross RRYY $\times$ rryy ?Parents: RRYY (round, yellow) $\times$ rryy (wrinkled, green). Gametes: RY and ry.
$F_1$: all RrYy, i.e. all round seeds with yellow cotyledons.
The $F_1$ plants form four kinds of gametes (RY, Ry, rY and ry) by independent assortment, and selfing gives the $F_2$.
$F_2$ phenotypes: round yellow, round green, wrinkled yellow and wrinkled green in the ratio 9 : 3 : 3 : 1.
So the $F_2$ never consists of only one phenotype; the three options beginning with 'Only' are wrong.
The remaining option names round seeds with yellow cotyledons and wrinkled seeds with yellow cotyledons, both of which do appear in the F2 (together with round green and wrinkled green).
So that is the answer intended by the paper, although the complete answer is all four phenotypes in the ratio 9 : 3 : 3 : 1.
That is every question in Principles of Inheritance and Variation for this filter.
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