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Cell Division Questions

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Cell Division Questions

Postby pimchy » Sat Apr 16, 2011 2:47 pm

A few multiple choice questions that I can't quite get my head around.
I've looked through lecture notes and my textbook to no avail :( in fact I'm somehow confusing myself more because multiple answers seem right to me.

(only one answer is correct out of each question)

Q1. The following list of events in the cell cycle is in the correct order:
a) Chromosomes align at equator, kinetochores attach to spindle fibres, cytokinesis, new nuclear membranes form.
b) Interphase, centrioles move to opposite poles, anaphase, chromosomes decondense.
c) Interphase, sister chromatids completely separate, kinetochores attach to spindle fibres, cytokinesis.
d) Chromosomes condense, DNA replication occurs, nuclear membrane breaks down, telophase.

Is (a) incorrect because the nuclear membrane forms before cytokinesis is complete?
(b) seems right to be as interphase occurs, then the centrioles move to opp poles in prophase, anaphase and the chromosomes decondense during telophase
(c) is not correct
(d) Do chromosomes condense or is it chromatin that condenses into chromosomes? or is that the same thing..? either way I don't think (d) is correct either

Q2. At the following stage of cell division the chromosomes are composed of two chromatids:
a) The G1 phase of a mitotic cell cycle.
b) Late anaphase of mitosis.
c) Late anaphase II of meiosis.
d) Telophase I of meiosis.

In anaphase of mitosis kinetochores pull daughter chromosomes towards opposite poles of the spindle.
I know that in late anaphase II the kinetochores detach from each other and sister chromatids pull apart to opposite poles to become individual chromosomes.
Telophase I (meiosis) is each chromosome still composed of 2 chromatids.
So option (d) seems right to me, but could someone explain in further detail or correct me if I'm not understanding something right?

Q3. An important outcome of meiosis II is the:
a) random assortment of homologous chromosomes
b) separation of homologous chromosomes
c) provision for crossing-over during prophase
d) separation of chromatids

Any help and/or explanation would be lovely thankyou! :)
pimchy
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Re: Cell Division Questions

Postby sully » Tue Apr 19, 2011 1:07 am

pimchy wrote:Is (a) incorrect because the nuclear membrane forms before cytokinesis is complete?


Yes, it reforms during telophase.

(b) seems right to be as interphase occurs, then the centrioles move to opp poles in prophase, anaphase and the chromosomes decondense during telophase


Correct- this is the right answer.

(d) Do chromosomes condense or is it chromatin that condenses into chromosomes? or is that the same thing..? either way I don't think (d) is correct either


I tried googling this and can't find an answer. Hopefully someone else can.

In anaphase of mitosis kinetochores pull daughter chromosomes towards opposite poles of the spindle.
I know that in late anaphase II the kinetochores detach from each other and sister chromatids pull apart to opposite poles to become individual chromosomes.
Telophase I (meiosis) is each chromosome still composed of 2 chromatids.
So option (d) seems right to me, but could someone explain in further detail or correct me if I'm not understanding something right?


You are correct! The homologous chromosomes are separated in meiosis I, and then the sister chromatids are separated in meiosis II (which is just like the process of mitosis.)

Q3. An important outcome of meiosis II is the:
a) random assortment of homologous chromosomes
b) separation of homologous chromosomes
c) provision for crossing-over during prophase
d) separation of chromatids


A- This happens in meiosis I.
B- Again, meiosis I. The homologous chromosomes pair up for crossing over during prophase I, and then are separated during anaphase I.
C- Meiosis I once more.
D- Correct. If you have a handle on mitosis, just think of that when you are asked about meiosis ii. In contrast, with meiosis I, the homologous chromosomes are still together. Their nonsister chromatids do crossing over in prophase I, and afterward the pairs line up randomly on the metaphase plate, which leads to genetic variability.

Hope this helps.
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Postby jwalin » Tue Apr 19, 2011 4:03 am

For Q2 D is right for in meiosis 1 there is a separation of homologous chromosomes and not chromatids.
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Postby pimchy » Tue Apr 19, 2011 2:32 pm

Thanks so much for the help :) definitely helped clear some things up for me.
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