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.
Since chromosomes typically come in pairs, I assume that the numbers indicate pairs of chromosomes. If this is true, then C would be the best answer.
I hope this helps. Thanks for asking.
To determine which answer is correct, we can analyze the information provided and compare it to the different options.
In meiosis, the chromosome number is halved, resulting in four cells with half the number of chromosomes as the original cell. In this case, the original marked cell had a chromosome number of 34 (17 + 17), and the resulting cells had chromosome numbers of 17, 17, 18, and 16. This indicates that something abnormal occurred during meiosis.
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 the abnormality occurred in the first meiotic division (also called meiosis I). However, the chromosome numbers in the resulting cells are not consistent with this option, as the chromosomes are not evenly distributed among the cells.
B) Synapsis did not occur properly in the second meiotic cell division but other events occurred as usual.
This option suggests that the abnormality occurred in the second meiotic division (also called meiosis II). However, the resulting chromosome numbers do not match this option, as there is an imbalance in the chromosome numbers among the cells.
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 an incorrect separation of homologous chromosomes occurred during the first meiotic division. The resulting chromosome numbers are consistent with this option, as two cells have the same chromosome number (17), indicating that they received the same homologous pair of chromosomes. Later, in the second meiotic division, the abnormal chromosome number (18 and 16) is observed. Thus, this option seems correct.
D) In the second meiotic division, one chromosome did not split apart but moved to one cell and later split.
This option suggests that an error occurred in the second meiotic division, where a chromosome did not separate correctly. However, the chromosome numbers do not align with this option, as there is an imbalance in the resulting cells' chromosome numbers.
From the information provided, option C seems to be the most likely answer. One homologous pair of chromosomes did not separate correctly in the first meiotic division but instead moved to one cell and later separated, resulting in the observed abnormal chromosome numbers in the four cells.