Bases and Hydrogen bonds

[jsmith613]

I have two questions
1) Why does adenine always pair thymine and cytosine always pair with guanine

2) why does the Cytosine-Guanine bond contain 3 hydrogen bonds whereas the adenine-thymine contain 2 hydrogen bonds

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I know about purine (A and G) and pyrimidine bases (T and c)
I know why A and G cant bond and why T and C cant bond but I don't get wh A cant bond with either C or T
the same applies for G.

I

[magicsiew]

U will find answers for all your question here

http://users.rcn.com/jkimball.ma.ultran ... iring.html