6.1 Reproduction

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Question 42
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In pea plants, the allele for purple flowers (PPP) is dominant over the allele for white flowers (ppp).

A scientist crossed a homozygous purple-flowered plant (genotype PPPPPP) with a homozygous white-flowered plant. All resulting F1 F_1\,F1​ offspring had purple flowers.

a.

State the genotype of the homozygous white-flowered parent plant.

[1]
b.

Two of the F1 F_1\,F1​ offspring plants (both with genotype PpPpPp) are crossed. Complete the genetic diagram (Punnett square) below by determining the missing genotypes of the offspring.

Male gamete: PMale gamete: pFemale gamete: PPP(i)Female gamete: p(ii)(iii) \begin{array}{c|c|c} & \text{Male gamete: } P & \text{Male gamete: } p \\ \hline \text{Female gamete: } P & PP & \text{(i)} \\ \hline \text{Female gamete: } p & \text{(ii)} & \text{(iii)} \end{array} Female gamete: PFemale gamete: p​Male gamete: PPP(ii)​Male gamete: p(i)(iii)​​

Identify the genotypes for (i), (ii), and (iii).

[2]
c.

State the expected ratio of purple-flowered plants to white-flowered plants in the offspring of this cross in its simplest form.

[2]

6.1 Reproduction Questions

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