Read the statment and then say which answer is right, why its right and why the others are wrong.
I think the answer might be D but I don't know how to explain it or if it is even right.
A biologist marked a cell which she knew was about to undergo meiosis. A short while later she observed the 4 cells produced by the original marked cell; their chromosomes numbers were 17,17,18,16. She knew these numbers indicated that something abnormal had occured during meiosis. Which of the following most likely occured:
A) One duplicated chromosome (composed of sister chromatids) did not split apart in the first miotic division.
B) Synapsis did not occur properly in the second meiotic cell division but other events occured as usual.
C) One homologous pair of chromosomes did not separate in the first meiotic cell division but moved to one cell and later separated.
D) In the second meiotic division one chromosome did not split apart but moved to one cell and later split.
I regret that we are not adequately staffed with biologists who can answer your question.
To determine the correct answer, let's break down the given information and analyze each answer choice:
The biologist observed 4 cells that were produced by the original marked cell. The chromosome numbers of these cells were 17, 17, 18, and 16. We are told that these numbers indicate something abnormal occurred during meiosis.
Now let's evaluate each answer choice:
A) One duplicated chromosome (composed of sister chromatids) did not split apart in the first meiotic division.
This answer suggests that during the first meiotic division, a duplicated chromosome, which should normally split apart, did not. However, this answer does not explain the difference in chromosome numbers observed in the 4 cells. Therefore, Answer A is not correct.
B) Synapsis did not occur properly in the second meiotic cell division, but other events occurred as usual.
Answer B suggests that during the second meiotic division, synapsis (the pairing of homologous chromosomes) did not occur properly. However, synapsis does not directly explain the difference in chromosome numbers observed in the 4 cells. Therefore, Answer B is not correct.
C) One homologous pair of chromosomes did not separate in the first meiotic cell division but moved to one cell and later separated.
This answer suggests that during the first meiotic division, one homologous pair of chromosomes did not separate as it should, but instead moved to one cell and later separated. This could explain the difference in chromosome numbers observed in the 4 cells. If one cell received both chromosomes from the non-separated pair, it would have 18 chromosomes, which matches one of the observed numbers. Therefore, Answer C is a possible explanation.
D) In the second meiotic division, one chromosome did not split apart but moved to one cell and later split.
Answer D suggests that during the second meiotic division, one chromosome did not split apart but moved to one cell and later split. This could explain the difference in chromosome numbers observed in the 4 cells. If one cell received an extra chromosome from the non-split chromosome, it would have 18 chromosomes, which matches one of the observed numbers. Therefore, Answer D is also a possible explanation.
Based on the information provided, both Answer C and Answer D are potential explanations for the abnormality observed during meiosis. However, without further information, it is impossible to definitively determine which answer is correct.