Question

Purple flowers versus red flowers and long pollen versus round pollen are two traits in a sweet pea plant. When a true breeding purple/long pollen plant is crossed with a true-breeding red/round pollen plant, the F1 generation offspring all have purple flowers and long pollen. When the F1 generation is bred to itself via human-directed fertilization, a ratio of 7 : 4.9 : 4.9 : 0.05, purple/long : red/long : purple/round : red/round is noted in the F2 generation. What is the most likely reason for this ratio?

Group of answer choices

The round pollen is less likely to fertilize the pea plants.

The genes for flower color and pollen shape are linked.

The red flower color is less likely to be noticed by bees.

The red color is a partially lethal allele.

Answer 1

The genes for flower color and pollen shape are linked

The 9:3:3:1 ratio expected from a dihybrid cross is for traits that assort independently. In these crosses, the Red color allele is linked to the round pollen allele and the Purple color allele is linked to the long pollen allele. In the F2 progeny proportion of 7:4.9:4.9:0.05, the cross favors the scenario where the plants are heterozygous for one trait and homozygous recessive for the other trait. This will only occur if the two traits are linked and being in the trans conformation would prefer the Heterozygous condition of the progeny.