Question

In sweet peas, the genes for flower color and pollen grain shape are 11 cM apart. A pure-breeding purple flowering plant with round pollen grains is crossed to a pure-breeding red flowering plant with long pollen grains. The resulting F1 offspring are all purple flowering plants with long pollen grains. What percent of offspring from a test cross analysis of the F1 individuals would you expect to be purple flowering plants with long pollen grains

Answer 1

The correct answer is - 44.5%.

Step-by-step explanation:

In this question, there are two traits are given, flower color and pollen shape. The purple flowers and long pollen are wild-type (dominant). Red flowers and round pollen are mutant or recessive. The cross is between a pure breeding purple and round pollen plant with red and long pollen plant. The offspring are all purple and long pollen plants. However, the offspring would be all heterozygotes genotype for both traits.

Linkage can be calculated as -

Linkage distance = % of recombinant offsprings formed in a test cross.

parental types are purple and long pollen, red and round pollen.

So, the recombinant type would be purple and round pollen, red and long pollen.

11% of the offspring would be recombinant type as the distance is 11cM. Therefore, 89% of the progeny would be parental type. Which means this 89% of parental offsprings have equal proportions of both phenotypes of parents. So, the purple flowers and long pollen would be half of 89%.

that is 89/2 = 44.5%.