Name: Sally
Status: Other
Grade: Other
Location: N/A
Country: United States
Date: February 2008
Question:
Why do not DNA bases form hydrogen bonds with cellular water?
Replies:
Bases are able to hydrogen bond water, but they'd rather bond with each
other. This is because the base-base bond in DNA is "thermodynamically
favored" (which basically means that all molecules are lazy, and it takes
more work for the bases to bond with water than it does to bond with
water). The structure of DNA also helps -- the DNA coils around itself,
and the backbone of DNA shields the bases somewhat from water. There are
enzymes that 'unzip' the DNA, and while the DNA is unzipped, it can bind
with sites on the enzyme or with other water molecules. Overall, DNA
that's zipped tends to stay zipped.
That's true at living temperatures. The answer changes when you heat up
DNA. If you boil the water the DNA is in, the DNA will uncoil and the
bases will bond with water instead of other bases. This is known as
'denaturing' -- it's a very useful fact that is used in PCR (polymerase
chain reaction) -- look it up!
NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.
