A question in Destroyer (#72)

[jjkim1232]

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#72
A somatic cell during interphase has been observed to have 10 chromosome. How many chromatid is this?

a)5
b)10
c)20
d)40
e)15

Destroyer's answer to this problem is c (20) because each chromosome would have two chromatids that are attatched at the centromere. However, chomotids (condensed version of chromatin) do not appear until Prophase....right?

So...the answer would be 10 chromosomes or 10 chromotins IN interpahse. And if the 10 chromosomes of interpahse has gone through the S phase...then it would be 20 chromosomes or 20 chromatins.

Am I wrong or is this question just poorly worded?


Thanks all

 

[shane.]

That's interesting that you've posted this question.

I came across this question earlier today and also had an issue.

The question states that the somatic cell is in interphase which consists of a growth phase, dna synthesis, then a second growth phase. The probelm should specify whether or not dna synthesis has occured, to double the genetic material present, should it not?

From the problem's solution, we are to assume that the chromasomes have replicated (by undergoing DNA synthesis) to produce 10 chromasomes each with a set of chromatids joined at their centromeres.

No?

 

[BoSox17]

Yep I was confused there a little too. I think it should be more specifically worded

 

[El Sol]

#72
A somatic cell during interphase has been observed to have 10 chromosome. How many chromatid is this?

a)5
b)10
c)20
d)40
e)15

Destroyer's answer to this problem is c (20) because each chromosome would have two chromatids that are attatched at the centromere. However, chomotids (condensed version of chromatin) do not appear until Prophase....right?

So...the answer would be 10 chromosomes or 10 chromotins IN interpahse. And if the 10 chromosomes of interpahse has gone through the S phase...then it would be 20 chromosomes or 20 chromatins.

Am I wrong or is this question just poorly worded?


Thanks all

Destroyer's answer is correct.

We're dealing with somatic cells so replication occurs via mitosis. During interphase each chromosome is replicated so that during division, a complete copy of the genome can be distributed to both daughter cells. After replication the chromosome consists of two identical sister chromatids held together by the centromere. No synapsis occurs since this is not meosis, which means that at the end of interphase there would be 20 chromatids, or 10 replicated chromosomes.

 

[jjkim1232]

Destroyer's answer is correct.

We're dealing with somatic cells so replication occurs via mitosis. During interphase each chromosome is replicated so that during division, a complete copy of the genome can be distributed to both daughter cells. After replication the chromosome consists of two identical sister chromatids held together by the centromere. No synapsis occurs since this is not meosis, which means that at the end of interphase there would be 20 chromatids, or 10 replicated chromosomes.

I am not sure I agree with you because:

Chromosomes do not condense and become chromotids until they reach Prophase. Chromosomes are not condensed and are called chromotins while in Interphase.

 

[TimeforDAT]

i'm not sure where i read this, i think it was in a book or somewhere..however chromatids are defined as replicated chromosomes. so then in prophase, where it would double its chromosomes would therefore have 20 chromatids.

 

[shane.]

If we're in interphase, how do we know we aren't in G1 phase?

 

[El Sol]

I am not sure I agree with you because:

Chromosomes do not condense and become chromotids until they reach Prophase. Chromosomes are not condensed and are called chromotins while in Interphase.

The question states that the chromosomes are already visible, and replication occurs during interphase, so you must have 20 chromatids. I know what you mean by chromosomes becoming visible during prophase, but the question tells you that you can discern 10 chromosomes during interphase, I guess you must assume that replication already occurred, leading to the 20 chromatid answer.

 

[Shunwei]

That's interesting that you've posted this question.

I came across this question earlier today and also had an issue.

The question states that the somatic cell is in interphase which consists of a growth phase, dna synthesis, then a second growth phase. The probelm should specify whether or not dna synthesis has occured, to double the genetic material present, should it not?

From the problem's solution, we are to assume that the chromasomes have replicated (by undergoing DNA synthesis) to produce 10 chromasomes each with a set of chromatids joined at their centromeres.

No?

Good point. I also think this question is poorly phrased. During interphase you have the G1, S, and G2 phases. This question needs to specify which phase of the cell one is talking about, or otherwise there is not clear answer.

 

[Clubby]

If you back off and think of the question and ask "what are they asking me", well they are obviously asking what happens in interphase. Well, the chromosomes split into sister chromatids, and double in number. 2 x 10 = 20. No need to look harder into the problem.

 

[shane.]

Jonathanaf, lolz0rz what song is that hotdog throwing down on the track in your avatar from?!?