Need help!! About base pairing.

[CyLMH]

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!!

[MrMistery]

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..

[sachin]

Me too never read about U replacing T in DNA.

It may deform DNA helix.

[druid]

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]

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.