does DNA change?
jumbuck at geocities.com
Sun Dec 22 02:30:37 EST 1996
vceinc at aol.com wrote:
> From the time a person is born until the time they die (hopefully to a
> ripe old age) does a person's DNA change. I know mutations occur, but,
> except for the mutations, do other changes occur?
> vceinc at aol.com
I don't remember the exact sequence (i can look it up if you like), but
each chromosome has a long chain of Adenine bases at the 5' end. When
the enzyme that duplicate the chromosome zip along, they get to the
poly-A chain and lose a few off the end - imagine a zipper that can't
quite inzip the last few teeth.
Other changes occur in the B-cells of the immune system. Antibodies are
made up of 3 distinct chains, each of which has thousands of possible
sequences. The genes coding for each of these sequences are laid end to
end. When the signal to produce a new antibody is received, all but one
of these sequences is spliced out randomly. the remaining sequences are
then used as the code for a new (novel) antibody. If this antibody fits
the target, the cell goes into replication mode, producing antibody
factories for that one antibody.
Some other cells in the body also use this "select one - chuck out the
rest" splicing method to produce a specific novel poroduct.
It's 1:30am and I'm remember coursework form 5years ago, so please
someone correct any gross mistakes i've made (I can never remember my 3'
from my 5' ends. etc)
otherwiose, hope it helps
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