Two heterozygous tall pea plants (Dd) are crossed. Tall is completely dominant. What fraction of the offspring are short?
Answer and explanation
Correct answer: D. 1/4
- Step 1: Dd x Dd gives DD : Dd : dd in the ratio 1 : 2 : 1.
- Step 2: Short plants are only dd, so the fraction is 1/4.
Answer
1/4.
Why not the others: 1/2: this is the fraction of heterozygous offspring. 3/4: this is the fraction of tall offspring. 0: heterozygous parents can still produce the recessive phenotype.
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