Xref: utzoo sci.psychology:159 sci.bio:1049
Path: utzoo!utgpu!water!watmath!clyde!att-cb!att-ih!pacbell!ames!ncar!boulder!eddy
From: eddy@boulder.Colorado.EDU (Sean Eddy)
Newsgroups: sci.psychology,sci.bio
Subject: Re: Evolutionary factors in human psychology
Message-ID: <5189@sigi.Colorado.EDU>
Date: 3 Apr 88 15:26:22 GMT
References: <764@actnyc.UUCP> <1093@bingvaxu.cc.binghamton.edu>
Sender: news@sigi.Colorado.EDU
Reply-To: eddy@boulder.Colorado.EDU (Sean Eddy)
Distribution: sci
Organization: University of Colorado, Boulder
Lines: 36

>In article <764@actnyc.UUCP> gcf@actnyc.UUCP (Gordon Fitch) writes:
>>I would think that there would be almost no neutral mutations at all.
>>If a mutation were otherwise neutral, i.e. noise, it would take up
>>room in limited genetic space (it must be limited, or "higher" species
>>would have indefinitely many genes.)  So "neutral" genes would be at
>>least moderately negative when the cost of storing and processing 
>>the information was thrown in, and would be eliminated before long.  

Two comments:

1) You assume that any mutation adds to the amount of information
that must be stored. In fact, many mutations are deletions or
substitutions of existing information.

2) You assume that space is limiting in a genome. In fact, this does
not seem to be so for higher organisms, which carry much more DNA
than necessary. An argument can be made that
the number of essential genes is limited (because of mutation rate)
but absolute genome size is not.

Neutral mutations should exist. For a trivial example, consider
a three-base codon in a protein coding gene. The sequence of this
codon is GGA, which is translated as a glycine in the protein.
Because the genetic code is degenerate (as are many geneticists),
glycine can also be encoded by GGG, GGU, or GGC; i.e., mutations
at the third position of the codon are "silent" and thus neutral. (To a first
approximation. Translational context effect buffs need not flame,
please.) 

- Sean Eddy
- Molecular/Cellular/Developmental Biology; U. of Colorado at Boulder
- eddy@boulder.colorado.EDU		!{hao,nbires}!boulder!eddy	
-
- "Love is a perky elf dancing a merry little jig and then suddenly
-  he turns on you with a miniature machine gun."
-                            - Kierkegaard (well, Matt Groening actually)