Why there is a double bond between A and T and a tripple bond between C and G in D N A structure?

Bonds between nitrogenous bases differ due to the kinds of bonds within them individually and the number of hydrogen bonds each is able to form. Looking at them two-dimensionally, it seems as though all should have triple bonds, but there aren't enough electrons available on the outer oxygen of thymine or the outer hydrogen of adenine. Those electrons have higher priority in the inner double bonds of the bases.





For a diagram of the nitrogenous bases, try http://student.ccbcmd.edu/~gkaiser/biotu...

Why there is a double bond between A and T and a tripple bond between C and G in D N A structure?
The two types of base pairs form different numbers of hydrogen bonds, AT forming two hydrogen bonds, and GC forming three hydrogen bonds (see figures, left). The GC base pair is therefore stronger than the AT base pair. As a result, it is both the percentage of GC base pairs and the overall length of a DNA double helix that determine the strength of the association between the two strands of DNA. Long DNA helices with a high GC content have stronger-interacting strands, while short helices with high AT content have weaker-interacting strands.[16]
Reply:No one knows but clearly there is a stonger bond between G and C - it may be a coincidence due to the purine and pyrimidne structure but evolutionary wise it had a function.





When you look at most genes in any organism the C-G tripple bonds are points where you would want the gene to hold together so it may just be that.





No definitive answer to this one im afraid but current research suggests its structurally as well as instructionally important.





T A double bonds tend to occur at the end of genes where they can easily swap over with other genes during recombination.

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