Questions re crossing over and histones

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dawn1070
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Questions re crossing over and histones

Post by dawn1070 » Wed Jun 16, 2010 6:41 am

A question I encountered is asking to demonstrate using a diagram of a bivalent of the F1 progeny with a single crossing over event causing all the produced gametes to be parental? I don't get how this works because I thought crossing over would have resulted in recombination no matter what?

Also why do prokaryotes not have histones surrounding their chromosome? I thought it was because there was only one chromosome, therefore space/tangling are less of an issue.

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JackBean
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Post by JackBean » Wed Jun 16, 2010 7:28 am

histones probably evolved later. However, to my knowledge, they have some histone-like proteins.

You could have also double crossing-over. Or crossing-over on other chromosome :lol:
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

dawn1070
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Re:

Post by dawn1070 » Wed Jun 16, 2010 8:06 am

JackBean wrote:histones probably evolved later. However, to my knowledge, they have some histone-like proteins.

You could have also double crossing-over. Or crossing-over on other chromosome :lol:

I'm looking at the question now and it is asking for a single crossing over event.

What do you mean by crossing over on other chromosome?

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Post by fastsandslash » Thu Jun 17, 2010 8:21 am

Ahh.. right. Most prokaryotes have a single loop of DNA, and we all know how hard it is to wind a rubber band (chromosome) around a ball (histone) and utterly pointless as yes, it only has 1 chromosome. Try unwinding it for protein synthesis... *shudders* I mean, good luck. Well, I'm quite sure JackBean was meaning, how about the *other* chromosomes crossed over, but *these* chromosomes are still the same as before :D. Assuming that parental means identical to parent chromosome, then my best bet would be that the alleles that recombined were identical in both parents (nigh impossible). So... uh. Yeah.

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