mitosis

[greenseeking]

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Please see attached.

Why isn't it B or even A??
Correct Answer is C

I'm just so confused. If 2n=4, then n=2. So wouldn't the chromosomes line up in a line, and get pulled apart. Then you would get 2 cells each with 4 chromatids, two from each parent. B?

Thanks in advance!

 

[SSerenity]

Adjacent Solid & Dashed lines = 1 double stranded DNA.

There is no reason to have any single stranded DNA running around, eliminating B.

This is Mitosis. We should be producing two identical daughter cells.
Option C shows just that.

Option D is meiosis and is not what we want.

 

[mehc012]

Please see attached.

Why isn't it B or even A??
Correct Answer is C

I'm just so confused. If 2n=4, then n=2. So wouldn't the chromosomes line up in a line, and get pulled apart. Then you would get 2 cells each with 4 chromatids, two from each parent. B?

Thanks in advance!

A cell undergoing mitosis ALWAYS has 2n chromosomes. It starts with 2n unduplicated chromosomes, then duplicates the DNA (which doesn't increase the number of chromosomes, it just takes each one from being a single chromatid to a chromatid pair), then splits the chromatids to result in 2 daughter cells, both with 2n unduplicated chromosomes.

It's mitosis: you end with 2 identical cells, each of which is identical to the parent cell. Aka answer C.

 

[greenseeking]

Hi everyone. Thanks for your replies.
I think I was confused because in the figure, you are starting with 2N duplicated DNA and at the end of telophase, you should see 2N DNA that are NOT duplicated (because the two copies are pulled apart at anaphase)

Answer choice C would be the result of mitosis after it has gone through S phase. I thought it was B because B would be left at the end of telophase and then after it goes through duplication of its chromsomes during S phase, you would get C. Can someone please clarify why my reasoning is wrong?

Thanks again!

 

[greenseeking]

in mitosis, you end with 2N and start with 2N. But you start with duplicated chromsomes (4C) and end with each chromsome in each cell (2C). That's what I was expecting to see in this problem.

 

[mehc012]

Hi everyone. Thanks for your replies.
I think I was confused because in the figure, you are starting with 2N duplicated DNA and at the end of telophase, you should see 2N DNA that are NOT duplicated (because the two copies are pulled apart at anaphase)

Answer choice C would be the result of mitosis after it has gone through S phase. I thought it was B because B would be left at the end of telophase and then after it goes through duplication of its chromsomes during S phase, you would get C. Can someone please clarify why my reasoning is wrong?

Thanks again!

They are not showing you the duplicated DNA. They are showing you double-stranded DNA, as in pre-duplication, single-chromatid, 2N cells. You start with 2N pieces of double-stranded DNA, and you should end with 2N pieces of double-stranded DNA.

 

[greenseeking]

thanks so much I get it now!!!