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RFLPs Theory

Keith Robison robison at mito.harvard.edu
Tue Nov 19 20:26:55 EST 1991

jhgillespie at ucdavis.edu (John Gillespie) writes:

>> 	I'm no expert in this area, but I'll give it a try.
>> 	For the most part, RFLPs behave as phenotypically-neutral Mendelian
>> co-dominant traits.

>I'm no expert either: exactly what IS the evidence that RFLPs behave as
>neutral traits?

Again, someone correct me if I'm wrong.

I don't know of any exhaustive look at this, but it is expected that most
RFLPs are neutral because:

1) The mode of testing them is an entirely artificial test
   (i.e. eukaryotic genes never naturally face prokaryotic restriction

2) Most of the RFLPs people look at are present in wild populations, and
   are presumed to have been fixed through random drift.

3) Most RFLPs are outside coding regions or other critical signals

On the other hand, inversions, insertions, re-arrangements, and deletions
are guaranteed to produce RFLPS, and some of these may not be neutral.
(In fact, the related technique of RAPDs -- I'll have to dig up the
reference -- relies on small deletions and insertions.  RAPD uses 
randomly selected PCR primers to amplify genome sections.  If your primers
happen to flank an insertion or deletion in one strain (versus another strain)
then the PCR products will show a length polymorphism).

Keith Robison   G1
Harvard University
Program in Biochemistry, Molecular, Cellular, and Developmental Biology

robison at nucleus.harvard.edu

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