The n + 1 female gametophytes (embryo sacs)produced by trisomic plants are usually more viable than the n + 1 male gametophytes (pollen grains).If 50% of the functional embryo sacs of a selfed trisomic plant are n + 1 but only 10% of the functional pollen grains are n + 1,what percentage of the offspring will be diploid?

Question

Quizplus · Accepted Answer

Since the trisomic plant selfed, it will produce 4 types of gametes: n, n+1, n+2, and n+3.

Out of the functional embryo sacs, 50% are n+1, which means half of the ovules will receive one extra set of chromosomes.

Out of the functional pollen grains, only 10% are n+1, so only a small proportion of the pollen will have an extra set of chromosomes.

When fertilization occurs between n+1 embryo sac and n pollen, it will produce triploid (2n+1) offspring.

Therefore, the percentage of diploid (2n) offspring will be (0.5 * 0.9) + (0.5 * 0.1 * 0.5) = 0.45 or 45%.

Hence, the best choice is C.

The N + 1 Female Gametophytes (Embryo Sacs)produced by Trisomic