http://www.bio.net/hypermail/MOLECULAR-EVOLUTION/lost of genes in primate
jeff at cher.heurikon.com
Sun Mar 3 21:51:34 EST 1996
In article <ralph.1176045731C at 220.127.116.11>,
R M Bernstein <ralph at ccit.arizona.edu> wrote:
>OK, i'll bite: What is an example of an organism that has more _coding_
>sequences but is considered less complex than another comperable organism
>with _less coding_ sequences.
Other than some examples that you could fairly classify as exceptions,
I cannot point to overwhelming evidence that the number of GENES (not
genome size) is uncorrelated with complexity -- so I'll yield to you.
The point of my original comment a few posts back was that the total DNA
content in a genome is unrelated to complexity, and that this phenomenon
is not explained by conventional evolution theory.
From: "Fundamentals of Molecular Evolution," by W-H Li and D Graur, 1991,
Sinauer Associates, Sunderland, MA.
"The C values in eukaryotes vary from 8.8 x 10^6 bp to 6.9 x 10^11 bp,
approx. 80,000-fold range. Unicellular protists, particularly sarcodine
amoebae, show the greatest variation in C values. The three amniote
classes (mammals, birds, and reptiles), on the contrary, are exceptional
among eukaryotes in their small variation in genome size (up to four-fold).
Other classes, for which a substantial body of C-value data exists, show
variation of at least 100-fold.
Interestingly, the huge interspecfic variation in genome sizes among
eukaryotes seems to bear no relationship to either organismic complexity
or the likely number of genes encoded by the organism. For example,
several unicellular protozoans possess much more DNA than mammals, which
are presumably more complex. Moreover, organisms that seem similar in
complexity (e.g., flies and locusts, onion and lily, paramecium aurelia
and P. caudatum) exhibit vastly different C values. This lack of
correspondence between C values and the presumed amount of genetic
information contained within genomes has become known in the literature
as the C-value paradox."
And from "The Cell" (Alberts, Bray, Lewis, Raff, Roberts, & Watson; 3rd
Figure 8-6 shows the "Lack of relationship between amount of DNA and
organism complexity. The amount of DNA in a haploid genome varies over
a 100,000-fold range from the smallest procaryotic cell -- the mycoplasma
-- to the large cells f some plants and amphibia. Note that the genome
size of humans is much smaller than that of many organisms that appear
to be simpler."
Sorry to put up so much -- I guess nobody here is arguing that this
situation does not exist.
Jeffrey Mattox -- jeff at heurikon.com
Cartoon of the day: http://www.heurikon.com
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