June 24, 2007

Where do DNAs go?




“Where have all the birds gone” used to be the plaintive cry of the environmentalists. Now neurobiologists are stunned by the mystery of the disappearing DNA. Many cells in the average brain may be missing huge chunks of genome say scientists and these emissive might decide our risk of disease.
Cells are generally assumed to need a full set of DNA to run with out major flow. In fact, a third set of dividing cells in one region of the adults mouse brain have gained or lost at least one chromosome, the same goes for 15% of the adult neuron these cells produce, biologists have discovered. This hints that every person’s brain may be a mosaic of cells with different genetic make-ups. The scientists working at university of California said they were stunned cells that gain or loss chromosomes could predispose of protect from certain disease, as speculated. Cells lacking chromosomes might also be prone to from tumors. Other scientists speculated that an increase 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 z1.
According to the scientists the cellular phenomenon thought to arise when chromosomes are divided up inaccurately at cell division must serve some biological purpose in the brain. Immune cells and blood cells appear not to show the same effect, so “it doesn’t seem to be mistake”. However, losing genes “changes what a nerve cell do”, they say perhaps slowing the speed at which they communicate. Some bacteria, for example, suffle genomes when they are in uncomfortable conditions, to create a new mutant that can survive. It is interesting that cells lacking the correct number of chromosomes in the growing embryo are carefully eliminated from the body’s tissue and embryo with chromosomes anomalies are often aborted spontaneously. Embryo and placenta sort from the some ball of cells yet according to placental diagnostic testing around 2% of placenta but not the embryos, they naturally contains a mixture of chromosomally normal and abnormal cells. At first normal any aberrant cells are mixed but about a third of the way through gestation they selected against and many commit suicide or be sorted into the placenta. The case appears to be a tangled or with tantalization clues, which will no doubt be solved in time. Till then one can only wonder at the mysteries of nature.

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