one copy Vs Two copies

Warren Gallin wgallin at
Thu Jun 22 15:52:27 EST 2000

fxl4 at wrote:
> Does anybody have a bright idea on how to tell the difference between one
> copy of a specific gene and two copies of it in the genome?Assuming that
> the genes are identical,you cannot apply Southern blot to tell the
> difference on RE fragments.

It would depend on what you mean by identical.  Southern blotting using
probes from the end of the gene would pick up differences in the
flanking sequence.  If you mean identical in the sense that a whole
block of DNA around your DNA is identical as well, then you would
probably have to go for some kind of extremely rare-cutting enzyme and
pulsed field electrophoresis.  Or keep cloning out from the identical
sequence until you encounter some sequence that is different between the
two copies.  If the two copies were at different positions in the
genome, FISH would show them up.

Warren Gallin
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