Why soemtimes polyacrylamide gels are used and not agarose gels to resolve DNA molecules?

Answer 1

You can read at

http://www.vivo.colostate.edu/hbooks/genetics/biotech/gels/principles.html

"Polyacrylamide gels have a rather small range of separation, but very high resolving power. In the case of DNA, polyacrylamide is used for separating fragments of less than about 500 bp. However, under appropriate conditions, fragments of DNA differing is length by a single base pair are easily resolved."

You can easily use agarose gel electrophoresis for <500 bp but you won't get as high resolution as with polyacrylamide.

Answer 2

What's the size of the DNA molecule you're running? Usually, polyacrylamide gels are used for proteins and have SDS to denature neutralize any charged groups. Agarose actually USES the charge on DNA to separate, or move, the molecule down the gel. I'd look at size and charge to determine that. Give me an example of where DNA is used on polyacrylamide.

Answer 3

Hi there! The type of enzyme used is called a restriction enzyme. They break down DNA into "chunks" of specific sizes. The short fragments are lighter and will travel more quickly through the gel. The buffer solution in the electrophoresis chamber keeps the pH balance (as buffers do in most chemical reactions). I hope that helps!