Percentage values commonly given for differences in DNA etc, may be meaningless.

Ludvig M€rtberg (
Fri, 26 Jul 1996 15:06:50 GMT

All the time we hear percentage values for how much species differ in
their genetic material. Yet there is unclear what people mean when
they for example say that humans share 98% or their genetic material
with chimpanzees. Is it sequence similarities? I have been thinking of
this and doubt if the "genetics" of an organism can be equated with
raw DNA sequence. Genome and genetic material may be difficult
concepts to define. Can they really be measured quantitatively, like
weight or length? Even relatively?

I suppose you can take melting temperatures from DNA-DNA
hybridizations and transform them into some basic idea of how much all
DNA sequences differ between two species, but you still don't know how
they differ. Is it point mutations, insertions/deletions, repetetive

Is there really an established way of measuring differences between
two DNA sequences that gives you a percentage value? If we take for
example a 100 bases and substitute 2, this may be a 2% difference. But
what if we insert 5 bases or delete 10, then what?

I'm bringing this up on sci.anthropology.paleo because people here
frequently talk about how we share this or that amount of genetic
material or DNA (given as percentage value) with different species
(60% with a banana!). I just want to remind you that it may not be a
correct way of showing differences between organisms.

Can we really talk about humans as the "third chimpanzee" because we
supposedly share 98% of our "genetic material"? Do we know what we are
talking about?

Ludvig M€rtberg