Question

Suppose you have two species of corn. One has sweet kernels and the other has large ears. Both have 20 chromosomes, each of which is homologous in both species. Suppose you want to create a hybrid that has both characteristics of sweet kernels and large ears, so you cross individuals from the two species. The initial hybrid you obtain has 20 chromosomes, but then you establish a viable tetraploid (4n) individual with 40 chromosomes. Which of the following could best explain this observation?

a. Nondisjunction of a single chromosome caused the doubling of the genome.
b. The initial F1 hybrid was unable to produce normal haploid gametes and instead produced diploid gametes. As a result, self-fertilization created progeny with 40 chromosomes.
c. The original F1 hybrid was able to produce normal gametes, thus, the tetraploid was formed by fusing one normal haploid gametes with an abnormal diploid gamete.
d. Nondisjunction of a random set of chromosomes produced abnormal gametes, and thus the 40 chromosomes represent a random assortment of chromosomes from the two parents.
e. None of the above can explain the phenomenon.

Answer 1

b. The initial F1 hybrid was unable to produce normal haploid gametes and instead produced diploid gametes. As a result, self-fertilization created progeny with 40 chromosomes.

Step-by-step explanation: