Country: United States
Date: November 2005
The question is regarding mutation of genes. The students
want to know when and where on the gene does mutation occur?
A mutation is a change in the base sequence of DNA...it was originally
defined for those protein coding parts of the DNA (gene)...as opposed to the
stretches of DNA that do not code for protein, but the more encompassing
definition is any change in the base sequence of DNA...With this in hand, a
mutation can occur anywhere on the chromosomal DNA. When, is another
matter. Mutations can occur anytime...during replication DNA polymerase can
make a mistake...not often. It can also occur following exposure to
radiation. UV light causes adjacent thymine bases (on the same strand)to
pair up...called thymine dimmers.
Mutations are any change in the DNA sequence. It can be as simple as a one
letter change, or as much as a whole part of a chromosome being lost, which
changes many genes at once. Mutations aren't always a bad thing-sometimes
the mutation occurs in part of the gene so that the protein's shape doesn't
change enough to effect its function. Other times, the one letter changes
the shape so drastically that it can't function at all. So it's hard to
say-there isn't one answer to your question.
But very basically-the DNA codes for amino acids which are in turn part of
a protein. The protein has a shape, let's say like a key. Also, for that
protein to work properly that shape needs to fit with something else, say
like a lock. If the key changes shape it won't fit in its lock any more and
can't do its job. But if the change is in the part of the key that doesn't
actually fit in the lock, it won't be as bad.
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Update: June 2012