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Old 06-08-2013
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Show Teeth Why stem cells not proliferating here?

Dyskeratosis congenital (DKC) is a genetically inherited disease in which the proliferative capacity of stem cells is markedly impaired. The defect has been traced to inadequate production of an enzyme needed for chromosome duplication in the nuclei of rapidly dividing cells.
Structural analysis has shown that the active site of this protein contains a single-stranded RNA that is required for normal catalytic function. Which step in DNA replication is most likely deficient in DKC patients?
A. Synthesis of centromeres
B. Synthesis of Okasaki fragments
C. Synthesis of RNA primers
D. Synthesis of telomeres
E. Removal of RNA primers

plz give expln. similar q may appear in exam imo, what say ?
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dr mumble (07-04-2013)

Old 06-08-2013
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Ans is D. Synthesis of telomeres.

DKC is a very rare congenital condition about 1 in a million so doubt it would come up. But hey as goljan says, now you know!

There are two types, Autosomal dominant which is associated with mutation in TERC (telomerase RNA component), while X-linked DKC is due to mutation in gene for dyskerin, involved in telomerase function as well.

The key point to note is that there is a mutation that affects TERC levels, which affects the normal function of telomerase, which maintains the telomeres. Remember telomerase preserves or protects the length of the telomeres (sequence of nontranscribed DNA at ends of chromosomes). So DNA would be prone to damage and so resulting in chromosome instability.

Source pubmed. (can't post the link so google DKC pubmed)

Hope that helps.
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dr mumble (07-04-2013), shoty (06-08-2013)


Molecular-Biology-, Step-1-Questions

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