"Al" wrote in message
...
A while back there was a discussion on this topic. Today's Washington
post
reports on an article published in Science, I think, that collected
genetic
samples from dog breeds and using genetic structures called
microsatellites,
they were able to identify which breed the sample came from with a 99%
accuracy.

What's a microsatellite?

What's the difference between a genus like Phalaenposis whose members will
interbreed and a single species like Canis familiaris which is highly
polymorphic. How is it determined that Phals are not like dogs but really
separate species? I know, I know....just speculate and enlighten. I will
not get involved in this discussion should one develop. I plan to read
along if it takes off on it's own but just sigh if it dyes without
comment.
"Diana Kulaga" wrote in message thlink.net...
The NY Times carried that story as well. I don't pretend to be a scientist,
but I did stay at a Holiday Inn.....

Microsatellites are simple repeated sequences in DNA such as
AGAGAGAGAGA. In general they have no particular function, but
because the replication machinery has problems with them,
accidents occur fairly frequently, so they vary in length between
individuals. This polymorphism is useful for gene mapping and
dog classifying operations.

It would be interesting to do a similar exercise in orchids,
but I suspect there's not much genome sequence data available.
I've just looked and there are over 300 sequence entries from
Phalaenopsis in GenBank, but they are largely ribosomal and
chloroplast sequences done by Tsai,C.C. and Chou,C.H. for a
taxonomic study which would be really interesting but as far
as I can see it's unpublished.

A species is one of those things that's obvious until you try
to define it in detail, and opinions do vary, and it is more
of a construct than a solid biological reality. The usual
species concept is that of a population which interbreeds in
nature (ie freakish crosses in captivity and reproductive barriers
caused by artificial selection don't count), but individual cases
are often unclear and subject to debate.

My feeling as a geneticist is that it doesn't take much to
cause hybrid sterility, possibly one incompatible gene in otherwise
closely related strains, or perhaps a chromosomal rearrangement.
This means the inability to interbreed is possibly not the most
useful criterion.

Leo