Bases and Hydrogen bonds

Genetics as it applies to evolution, molecular biology, and medical aspects.
New forum link:

Moderators: honeev, Leonid, amiradm, BioTeam

The new Biology Online has arrived!

We are very pleased to announce the website's new design and features. As a biology website pioneer in 2001, it has grown to become the world's most comprehensive online database for biology terms and topics. Thus, we would like to invite you to take part in this significant milestone by checking out these latest features from Biology Online.

Biology Dictionary

The largest online biology dictionary with over 70,000 biology terms! Learn various topics, concepts, and principles in biology. Start by searching here.

Biology Articles

Get the latest biology news, insights, trends and discoveries in biology and other related research fields. We have over 5,000 articles you can choose from.

Biology Tutorials

From the basics to the more advanced lessons, our tutorials will help you learn various topics in biology. Browse from over 100 free biology lessons here.

New Biology Forum

We hold one of the largest discussion boards in biology online! Join our community by signing up here or log in here if you already registered with us before.

Thank you and we hope you will join us as the site continues to grow by leaps and bounds.

Biology Online Team

Posts: 31
Joined: Sat Jul 25, 2009 9:37 pm

Bases and Hydrogen bonds

Post by jsmith613 » Fri Jan 07, 2011 3:46 pm

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

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.


Posts: 145
Joined: Sun Jan 24, 2010 3:07 pm

Post by magicsiew » Fri Jan 07, 2011 4:17 pm

U will find answers for all your question here ... iring.html