MadSci Network: Molecular Biology

Re: How do scientists receive the genetic information in organisms since the RN

Date: Sat Jul 24 00:04:42 1999
Posted By: Peter Pearson, Cryptologist
Area of science: Molecular Biology
ID: 924102148.Mb

Molecular biologists (of which, I must confess, I am not one)
have the coolest collection of clever tricks of any major
profession today. If you keep asking this question, you'll
hear of a lot of amazing techniques.

Scientists studying DNA are usually looking not at single
molecules but at large numbers of molecules. By staining
DNA with fluorescent dyes, you can tell (roughly) how
much DNA is at various spots on a thin sheet of jellylike
agarose gel.

If you push the DNA down the sheet of gel with an
electric field, the shorter pieces move faster than
the longer pieces. So now you can tell how much DNA
you have in pieces of various lengths.

"Restriction enzymes," discovered in bacteria, snip
DNA molecules at places where the sequence of DNA bases
matches some particular pattern. If you expose some DNA
to a restriction enzyme and then "run it on a gel," the
lengths of the DNA snippets tell you the spacings between
the patterns that the restriction enzyme recognizes.

If you start making a lot of copies of a piece of DNA,
but "poison" the process with a poison that will sometimes
stop the copying when a Guanine base is being added to
the new DNA molecule, the lengths of the resulting strands
tell you exactly how far from the beginning of the DNA
molecule the Guanine bases appear.

And so forth, with trick after trick. If you want even
cleverer tricks, ask about the Polymerase Chain Reaction.

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