From: justinf@cco.caltech.edu (Justin Fang)
Newsgroups: talk.origins
Subject: Re: Evolution implied by the Bible
Followup-To: talk.origins
Date: 10 Jan 1993 07:19:01 GMT
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In article <1imcqnINN4va@uniwa.uwa.edu.au>, hartley@maths.uwa.oz.au (Mike
Hartley) wrote:
[stuff deleted]
> 
> The amount of genetic information `inside' an individual can not
> be directly inferred from the individual's external appearence.

What do you mean by "information"? All normal humans have 46 chromosomes,
and the same number of genes.

> A person may `have' genes for producing brown hair, blonde hair and
> red hair, but that doesn't mean their hair will be stripy.

Er, no. You seem to be confusing genes, which are particular pieces of DNA
at particular locations on chromosomes, (they're sort of like variables)
and alleles, which are particular values for those "variables". Remember
that for any particular gene, an individual can have only two different
"values" or alleles. Hair color is, I believe, coded for by several genes.
For instance, you'd have one that codes for the amount of a red pigment in
your hair, another for the amount of a brown pigment, etc. For each of
these genes, you'd have two possible values, of which one would be
dominant. Your hair color would be determined by the dominant values for
each gene. (It's probably more complicated than this. If anyone knows
exactly how it works, tell me.)
 
> Now consider an individual who possesses a wide variety of genes
> for most of their characteristics - perhaps from the wild. It may
> be possible to take this individual, and by selective breeding, produce
> a number of other individuals - eg Great Danes and Poodles. How might
> one do this?
> 
> Say we want to produce a poodle. Take the original dog, and begin to
> breed it up. Select those of its offspring which are more `poodle-like'.
> So we consistently pick the smaller dogs of the litters. We do this for
> several generations, and our `proto-poodles' are getting smaller and
> smaller. Suddenly, a dog is born with curly hair. "Wow!" you exclaim.
> I'll keep that one! Fairly soon, all of your dogs have curly hair,
> and so you continue.

Not as I understand selective breeding. A poodle would not "suddenly" be
born with curly hair. Rather, the same process would be employed as was
used to reduce the size of the dog: you look for dogs which have, through
random chance mutations, alleles coding for slighly curly hair and breed
those, pick the offspring with the curliest hair, and continue. This is
obviouly not a quick process, which is the attraction of genetic
engeneering.
 
> Where did the curly hair come from? The study of genetics tells us that
> it was there all the time in the `mongrelised' individuals, but being
> a recessive gene, only became manifest under certain (rare) conditions.

You seem to have studied different genetics than I have. 

> Where did the straight hair go? Well, since it's a dominant gene, it's
> obviously not present at all in the poodle. (NB - I do not know for
> certain if straight hair is dominant or curly hair recessive in dogs.
> Nonetheless, the general principles still apply). 
> 
> So, we see that the poodle `contains' a lot less genetic information
> than our initial dog.

No. It contains EXACTLY the same amount of genetic information -- it's just
different information.

> Although it is possible, by selective breeding
> to so reduce the genetic variation of an individual, it is not possible
> to increase the individuals `mongrelisation'. So, if you wanted to
> produce a great dane, you should go back to the original stock,
> and forget about the poodles. The poodles, so `purebred', may simply
> be utterly useless as a breeding stock for great danes, as they may
> not have the genetic information for producing (for example) the right
> kind of ears, or even for producing the correct size! 

The reason you wouldn't try to get great danes from poodles is not that
it's impossible, just that it would take a LONG time, and you'd be far
better off starting with individuals who are already close to your goal.
 
> This fact is known amongst biologists. Agricultural Technologists,
> when trying to produce "new" species of wheat (for example if the
> commonly used ones are suddenly found to be susceptible to 
> particular diseases), don't bother with the (readily available) 
> `purebred' wheat which is on the general market, but instead
> search high and low for the wild (less purebred) varieties, which
> are more likely to have the genetic information needed to provide 
> resistance to the disease.

Actually, they are looking for varieties of wheat which, just by chance,
happen to have, for instance, alleles conferring resistance to some disease
that the commonly used varieties don't.
 
> Now consider the original stock of a species. It may have a high
> degree of genetic variation, but natural selection will tend to
> reduce this with time, possibly almost eliminating some of the
> dominant alleles and allowing the recessive ones to manifest, 
> producing what appear to be new characteristics (Eg - the Galapagos 
> finches).

Are you saying the "original" finch had all of the alleles that are
displayed by Galapagos finches now? That's a lot of different
alleles...remember, any given individual can have only two of the many
possible alleles for each gene. Also, where did the "original" finch come
from? I assume you're saying it was created... 
 
[stuff deleted]
> Yours, Mike H...
> --
> Michael Hartley 		    _-_|\  | "All things works for good to
> hartley@madvax.maths.uwa.oz.au     /	 \ |  them that love God - them that
> University of WA ----------------> *_.-._/ |  are the called according to His
> 					v  |  purpose" - Romans 8:28

Justin Fang (justinf@cco.caltech.edu)

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Newsgroups: talk.origins