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Simple Q on chromosomes

PB HULBERT P.B.Hulbert at bradford.ac.uk
Thu May 25 08:40:18 EST 1995


PB HULBERT (P.B.Hulbert at bradford.ac.uk) wrote:

: Is there just one strand (extremely long) of DNA in a single human Chromosome?
: I ask because some books show a chromosome as a structure with 4 'arms' -
: 2 short and 2 long - with bands which can be shown up by biological stains.
: These pictures seem to show symmetrical staining on the 2 similar arms eg
: on the long arms.  Does that mean that the 2 arms are completely identical
: at the chemical sequence level? If so, are there 2 stands of DNA in each
: chromosome? (one in each arm).
: More biochemical books show  the DNA of the Chromosome as a single 'line'
: pinched in at the 'waist', with marked sites at which endonucleases act.

: Please explain simply, to put me out of my misery !
: --Peter Hulbert, ---p.b.hulbert at bradford.ac.uk
: Thanks.
Thanks for the replies I received. I had not understood that the 'X'
pictures corresponded to the dividing state when there was twice as much
DNA per cell than normal.
Thanks again --Peter--



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