Need help!! About base pairing.

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CyLMH
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Need help!! About base pairing.

Post by CyLMH » Tue Oct 31, 2006 4:56 pm

I met this problem in the tutorial,

why U cannot replace T in the DNA double helix?

I guess it might be because the distance may be different (not 1.08nm, as is the distance of A-T & C-G pairs).

Anyone can give specific explanation?

Thx a lot!!

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MrMistery
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Post by MrMistery » Tue Oct 31, 2006 6:15 pm

i've always thought that the DNA polymerase can only work with T, not U... I never actually read this anywhere, so i may be wrong..
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sachin
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Post by sachin » Tue Oct 31, 2006 7:04 pm

Me too never read about U replacing T in DNA.

It may deform DNA helix. :?:
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Post by druid » Tue Oct 31, 2006 9:23 pm

Any uracil found in DNA is removed by mismatch repair system.

"One of the most common reactions in which a base is directly removed from DNA is catalyzed by uracyl-DNA glycosylase. Uracil occurs in DNA most typically bacuase of ( spontaneous ) deamination of cytosine. It is recognised by glycosylase and removed"

Genes VIII, Lewin, p451

CyLMH
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Post by CyLMH » Wed Nov 01, 2006 11:45 am

druid wrote:Any uracil found in DNA is removed by mismatch repair system.

"One of the most common reactions in which a base is directly removed from DNA is catalyzed by uracyl-DNA glycosylase. Uracil occurs in DNA most typically bacuase of ( spontaneous ) deamination of cytosine. It is recognised by glycosylase and removed"

Genes VIII, Lewin, p451


Ok, thx. I guess this is the answer. I asked one of my schoolmate, and he gave me a similar answer.

Because U has a similar structure to C, so it will be corrected to C if it is in the DNA structure. For the reason above, it cannot be present in DNA.

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