DNA Structure and Replication

ID #1107

I am a bit confused by DNA denaturation. I understand that the hydrogen bonds between opposite base pairs break, breaking the double helix. However, I do not understand how base stacking interactions are involved in the 2 helices breaking at all. Don't these hydrophobic interactions just work within one strand of the helix?

Remember our first lecture on biomembranes, when we described the spontaneous formation of liposomes because the edges of a planar bilayer are still exposed to water? Conceptually, the same thing is going on here. There are certainly hydrophobic interactions between adjacent bases on an individual strand, but there are also a lot of water molecules lining up along that edge. So DNA tends to adopt a double-helical structure, which among other things hides the hydrophobic bases. To denature DNA, you have to get past these forces too, although that's not typically as much of a contribution as the hydrogen bonding. In fact, hydrogen bonds are usually the only factor people talk about when describing DNA denaturation. In case you're curious, RNA would be double stranded too if A) it had a complementary strand to base pair with, and B) it wasn't bound by so many proteins, as we'll see in future lectures.

Print this record Print this record
Send to a friend Send to a friend
Show this as PDF file Show this as PDF file
Export as XML-File Export as XML-File