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Mutation Clarification
Name: John
Status: Other
Grade: 12+
Location: NJ
Country: United States
Date: Summer 2009
Question:
Are mutations [like the increase in number of limbs on a
frog an example of] an increase in genetic information to a genome?
If not, what is it?
Replies:
Hi John,
A lot of terms you used seem to be used incorrectly, so I want to start with
some definitions.
First, a mutation refers to a change in genetic information (the actual base pairs of
DNA). Traits like "number of legs" or "color of eyes" result from genes, which are
made up of DNA. A changes in the DNA sequence (also called genotype) can result in a
different trait (although not always). However, the trait itself would not be called
a mutation -- the trait is what results from the mutation.
Also, there is not a direct link between "amount of DNA" and "number of [whatever]"
trait. When a frog is born with double-limbs, it does not mean that the frog's genome
doubled, or that the "leg gene" doubled. More than likely there was some problem in
the frog's development (which could be genetic or could be some environmental factor).
There is not a one-to-one relationship between a trait and a gene; for example,
humans have two eyes, but that doesn't mean we have two "eye genes". Likewise, we
don't have 100,000 copies of a "hair" gene for every hair on our body, etc. etc.
Last, I am stumbling a little bit over one of the terms you used -- "an increase in
genetic information" is problematic to define.
If you simply mean the number of base pairs, than increases in genetic information
happen all the time -- mutations can cause duplications of genetic information,
resulting in more base pairs. These mutations can also result in evolutionary
advantages (for example, read about color vision --
http://en.wikipedia.org/wiki/Evolution_of_color_vision_in_primates).
I could imagine trying to define "an increase in genetic information" related to
phenotypes (expressed traits) or some qualitative or quantitative assessment of the
'advantage' of the traits. All of these have problems though too. More mathematically,
one can describe the complexity of a string of digits, although there is no direct
relationship between mathematical complexity of genetic code and biological traits.
As a hypothetical example, let's suppose you combine a mutation that duplicates a
gene, and some random mutation. Let's assume this process keeps occurring without
natural selection. Over time you would build a great deal of (mathematical) complexity.
The pressure of natural selection would serve to reduce the frequency of this, but it
does happen (see vision, above).
I do recall having heard a line of reasoning based on a misapplication of the second
law of thermodynamics (it dealt with entropy and information theory) to argue that
biological diversity cannot emerge without God. After reading your question, I did
a little internet searching and re-discovered some of these claims. The best short
answer I can give you is that this line of reasoning is fundamentally flawed.
"Entropy" is *not* a synonym with "randomness" or "disorder". I'm not sure if this
is what you were asking about, so feel free to respond if you want more information
on this topic.
Hope this helps,
Burr
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Update: June 2012
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