[MOL] DNA, Aging and Cancer, Part 1.... [00164] Medicine On Line

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[MOL] DNA, Aging and Cancer, Part 1....

DNA, Aging and Cancer, Part 1
by: Darryl See M.D. and Ferre Akbarpour, M.D.

Excerpt from the soon to be released book Anti-Aging: The Quest to End Aging

DNA is the fundamental molecule of life. It occurs in all cells. DNA stores genetic information in double helical chains that wind about each other like a double spiral staircase. Its structure is similar to that of the caduceus: the winged staff with two serpents twined about it, carried by the Greek god Hermes and used as the symbol of the medical profession.

Pairs of four different bases—adenine, paired always with thymine, and cytosine, paired always with guanine—form the steps that link the two intertwined strands. These four bases, or nucleotides, as they are often called, are usually abbreviated “A and T,” “C and G.”

The four nucleotides can appear in any sequence or order, and one or more of them may be repeated any number of times, as long as each is always paired with its partner in the complementary strand. The number of different combinations that can be expressed, or created, in this four-letter alphabet is virtually unlimited: four to the Nth power, where N is the number of base pairs. Considering that the DNA in human cells contains about three billion base pairs, this gives us a potential of different possible DNA combinations as four raised to the three-billionth power —a very large number indeed.

When wound around itself many times (super-coiled), DNA takes on a sort of crooked sausage shape we call a chromosome—the basic unit of heredity. All somatic human cells have 46 chromosomes. One set of 22 is inherited from the mother; a matching set comes from the father. An additional pair of chromosomes determines the sex of the baby. An XX combination results in a girl; an XY pairing results in a boy.

DNA holds the instructions for the proteins necessary for creating and maintaining life. The segment of DNA that specifies (codes for) one complete protein is called a gene.

Proteins are made of amino acids. The type of protein that is created by a group of amino acids is determined by their order in its formation. The order of amino acids is specified by the sequence, or order, of consecutive groups of three-nucleotide units, called triplets or codons, found within the gene for that protein. For example, the triplet CCT is the code for the amino acid glycine. CAA is the codon for the amino acid valine. AGA codes for serine. And so on, until the sequence of amino acids that determines the primary structure of the protein is complete. Ultimately, this amino acid sequence determines the three-dimensional shape (and hence the function) of the protein molecule.

The process continues. The next gene holds the genetic code for the next protein. And so on, for the next protein, and the next, until every single atom of every single protein that comprises an organism has been completely and precisely specified. This complete set of genes is like a library that holds a blueprint, or recipe, for making each kind of molecule the organism needs. It is its genome.

What has all this to do with cancer or aging? Well, quite a lot, as it turns out
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