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Why do chromosomal deletions occur more at certain regions?

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Why do chromosomal deletions occur more at certain regions?

Postby Lucanus cervus » Wed Jan 12, 2011 2:36 am

I have my genetics exam tommorow and I can't find the answer to the following question:

Why do chromosomal deletion occur more at certain regions of chromosomes?

So deletions of segments of dna in chromosomes can be due to

1) errors in repair of double strand breaks
2) Crossing over between repetitive dna segments



Is it that they occur with higher frequency in regions with a great amount of repetitive DNA sequences?

But there must be other reasons?


Please help me

Thans in advance,

Sam
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Postby kolean » Thu Jan 13, 2011 2:52 pm

Another one would be chromatin modeling. When DNA is exposed as single strands/double strands being temporarily separated, then a break or base pairs pairing up (especially at repetitive sequences - loops back on itself - and can then be either excised out or stays looped during DNA strand synthesis and is not replicated) can happen more easily. Nucleosomes keep the DNA tightly packaged, and the accessory proteins and regulatory RNA protect the DNA.
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