How is crossing over different than simply receiving a particular allele from each parent?
1 answer:
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Answer:
50%
Explanation:
According to this question involving a gene coding for seed shape in pea plant, the allele for round seeds (R) is dominant to the allele for wrinkled seeds (r). This means that a heterozygous pea plant (Rr) will have a round seed shape.
If a plant that is heterozygous for seed type (Rr) is crossed with one that has only homzygous wrinkled seeds (rr), the following gametes will be produced by each parent plant:
Rr - R and r
rr - r and r
Using these gametes in a punnet square (see attached image), the following proportions of offsprings will be produced:
Rr, Rr, rr and rr
Rr = round seed offsprings
rr = wrinkled seed offsprings
Since 1 out of 2 offsprings has wrinkled seeds, 1/2 × 100 = 50% is the percentage of offsprings expected to have wrinkled seeds.
