A potato has a diploid number of 48.If an egg of this plant is found to have 23 chromosomes,the most likely explanation is that
A) normal meiosis has occurred.
B) nondisjunction occurred during meiosis I.
C) normal mitosis has occurred.
D) nondisjunction occurred during mitosis.
E) crossing over occurred during meiosis I.

Question

Quizplus · Accepted Answer

If the diploid number of the plant is 48, then the haploid (n) number would be 24. If an egg is found to have 23 chromosomes, then it is missing one chromosome, which could have been lost during meiosis I due to nondisjunction. This means that one daughter cell would have received an extra chromosome, while the other daughter cell would have received one less chromosome, resulting in an egg with 23 chromosomes instead of 24. Normal meiosis would have resulted in four haploid daughter cells with 24 chromosomes each, and normal mitosis would have resulted in two diploid daughter cells with 48 chromosomes each, so options A and C can be ruled out. Nondisjunction is not likely to occur during mitosis, as mitosis results in identical daughter cells and does not involve the separation of homologous chromosomes, so option D can be ruled out. Crossing over during meiosis I would not result in a change in the number of chromosomes in the egg, so option E can be ruled out.

A Potato Has a Diploid Number of 48