jdd@allegra.UUCP (John DeTreville) (08/13/84)
I have what I feel sure is a foolish query, but I don't know the answer.
I know that genetic information is stored in chromosomes, and I know that
genetic information is stored in DNA, and I can't understand how these can
both be right.
So, can someone explain things to me?
Cheers,
John ("Not So Hot On The Physical Sciences") DeTreville
Bell Labs, Murray Hilljdd@allegra.UUCP (John DeTreville) (08/14/84)
Thanks for the many replies on my recent query about the relation between
chromosomes and DNA (and thank everyone for \not/ just posting it!).
I received replies from (in alphabetical order) Mark Biggar, Matt Crawford,
Richard Goldschmidt, Les Gondor, Berry Kercheval, Stan King, Pat Parseghian,
Donn Seeley and Robert Thau.
The low-level answer is "Simple. Chromosomes are composed of DNA." ("Like
beer comes in six-packs, and beer comes in cans.")
The medium-level answer is "The chromosome is the DNA plus some proteins
(histones) to give it some structure. Leaving a long molecule loose
would increase the chances of it becoming tangled or broken, so the histones
act as spools upon which the DNA is wound."
The high-level answer is that "chromosomes are structures of protein around
which are wound tangled strings of DNA. You get several levels of
structure, starting with the famous double helix (a double strand of DNA
wound up like a telephone cord), then helices of helices all the way up to
peculiarly shaped knobs and then finally the macroscopic (but still
microscopic) X-shape that you see with optical microscopes. The funny
configuration is laid out so that various stretches of DNA ('genes') can
easily be turned off or on for the purpose of copying off pieces which store
useful information such as protein templates. I seem to remember a nice,
layman-oriented article on DNA structure in Scientific American a few years
back."
Cheers,
John ("Now That I Know This, What Can I Use It For?") DeTreville
Ball Labs, Murray Hill