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.
Please only post your questions once. Repeating posts will not get a quicker response. In addition, it wastes our time looking over reposts that have already been answered in a previous post. See you previous post. Thank you.
To determine which answer is correct, let's analyze each option:
A) One duplicated chromosome (composed of sister chromatids) did not split apart in the first meiotic division.
This option suggests that a duplicated chromosome did not separate during the first meiotic division. However, the chromosome numbers observed in the cells (17, 17, 18, 16) do not support this possibility as the number of chromosomes should be equal in all cells. Therefore, option A is unlikely to be the correct answer.
B) Synapsis did not occur properly in the second meiotic cell division but other events occurred as usual.
Synapsis refers to the pairing of homologous chromosomes during meiosis. The given chromosome numbers (17, 17, 18, 16) do not provide any evidence of improper synapsis, as the numbers are not consistent with this scenario. Therefore, option B is also unlikely to be the correct answer.
C) One homologous pair of chromosomes did not separate in the first meiotic cell division but moved to one cell and later separated.
This option suggests that one pair of homologous chromosomes did not separate during the first meiotic division but later separated. The resulting chromosome numbers (17, 17, 18, 16) support the possibility of a non-disjunction event where one cell received both homologous chromosomes, resulting in a cell with 18 chromosomes instead of the expected 17. This scenario is consistent with the observed chromosome numbers, making option C a plausible answer.
D) In the second meiotic division, one chromosome did not split apart but moved to one cell and later split.
According to this option, one chromosome failed to separate during the second meiotic division but later split. The chromosome numbers observed (17, 17, 18, 16) do not align with this scenario, as the numbers would not be expected to differ between cells in this manner. Therefore, option D is unlikely to be the correct answer.
Based on the information provided, option C is the most likely to have occurred. It suggests that a non-disjunction event during the first meiotic division resulted in one cell receiving an extra chromosome.
Remember, it's important to carefully analyze the information given in the statement and relate it to the options provided to determine the correct answer.