Brains mislay Genetic Material

[Guest guest]

Cells are generally assumed to need a full set of DNA to run without major

flaws, but the following study shows that this is not necessarily true even

in an organ as sophisticated as the brain.

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<http://dx.doi.org/10.1073/pnas.231487398>

American Society for Cell Biology, San Francisco, Dec, 2002

Brains may be Genetic Mosaics

Nerve cells mysteriously mislay chromosomes.

HELEN PEARSON

[Excerpts given ...]

Many cells in the average brain may be missing huge chunks of genome,

scientists revealed at a San Francisco meeting yesterday. The puzzling

omissions might decide our risk of disease.

Cells are generally assumed to need a full set of DNA to run without major

flaws. In fact, a third of dividing cells in one region of the adult mouse

brain have gained or lost at least one chromosome - the same goes for up to

15% of the adult neurons these cells produce, biologists have discovered.

This hints that every person's brain may be a mosaic of cells with different

genetic make-ups. " We were stunned, " said Dhruv Kaushal of the University of

California at San Diego at the American Society for Cell Biology conference.

" We want to know what this means for the brain. "

Cells that gain or lose chromosomes could predispose or protect from certain

diseases, speculates Kaushal. Down syndrome symptoms, for example, might be

lessened in patients who have frequently lost the extra copy of chromosome 21

that is responsible for the disorder.

Cells lacking chromosomes might also be prone to form tumours. And some

scientists speculate that an increased risk of developing Alzheimer's disease

might arise in otherwise healthy people who carry a subset of brain cells

with an extra copy of chromosome 21......

Team member Mike McConnell argues that the cellular phenomenon - thought to

arise when chromosomes are divvied up inaccurately at cell division - must

serve some biological purpose in the brain. Immune cells and blood cells they

have examined appear not to show the same effect, so " It doesn't seem to be a

mistake " .....

Losing genes " changes what a [nerve] cell can do, " says McConnell, perhaps

slowing the speed that they communicate. Some bacteria, for example, shuffle

their genomes when they are in uncomfortable conditions, to create a new

mutant that can survive.........

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Dr Mel C Siff

Denver, USA

http://groups.yahoo.com/group/Supertraining/