What is DNA?

Short for deoxyribonucleic acid, DNA is the building block for our chromosomes. It is made up of just 4 nucleic acids: adenine, thymine, cytosine, and guanine. Adenine is always paired with thymine and cytosine is always paired with guanine. There are 23 pairs of chromosomes, for a total of 46 chromosomes, in every cell in human beings. That genetic material is found in the nucleus or command center of every cell in our bodies. In essence, the DNA in the chromosome is the blue print for humans. Those instructions are packaged in genes which are basically sequences of DNA. Those genes code for everything from hair color to personality, from baldness to obesity, from musical ability to longevity. The DNA which is expressed in these gene sequences in many ways determines the destiny, or shall we say potential, for an individual. Understandably, one’s environment and choices affect outcomes, but the DNA is very powerful.

The human genome, which is the entire collection of genes found in a single set of chromosomes (or all of the DNA in an organism), consists of 3.2 billion nucleotide pairs or bases. To get some idea about how much information is packed into a very tiny space, a single large gene may consist of tens of thousands of nucleotides or bases, and a single chromosome may contain as many as one million nucleotide base pairs and four thousand genes. What is most important about these pairs of bases is the particular order of the As, Ts, Gs, and Cs. Their order dictates whether an organism is a human being, a bumblebee, or an apple. Another way of looking at the size of the human genome present in each of our cells is to consider the following phone book analogy. If the DNA sequence of the human genome were compiled in books, 200 volumes the size of the Manhattan telephone book (1,000 pages) would be needed to hold it all. This would take 9.5 years to read aloud without stopping. In actuality, since the human genome is 3.2 billion base pairs long, it will take 3 gigabytes of computer data storage to hold it all.

Aging is thought to be faulty copying of DNA when cells divide. If all the genetic material is not duplicated perfectly, then the instructions for the cell are not understood and followed properly. The error is further compounded after the next division. After a while, the copy of the copy becomes more distorted, not unlike the progressive fuzziness produced from a copier machine when the original is not used. It has been discovered that the end of the chromosome, or the telomere, is crucial to the proper division of the cell.