DNA explained for the layman

     Human reproduction is based on the incredibly complex chemical compound known as DNA (deoxyribonucleic acid), which carries all of the genetic assembly, maintenance, and functional information for the human body, different and distinct for each individual human body, with the entire code present in every cell of the human body (except of course, the reproductive cells, which carry one-half of the genetic information.)

     The genetic information carried in DNA is coded using a sequence of four bases (adenine, guanine, cytosine, and thymine) arranged in pairs on opposing helical strands with molecular weights in the millions.  The number and sequence of base pairs enables millions of instruction to be encoded in each DNA strand.  This structure is simple and complex at the same time and its elucidation won the 1962 Nobel Prize in physiology and medicine for James D. Watson and Francis Crick.

   Strand-like paired structures (twenty three pairs of chromosomes in normal humans) found in human body cells each carry millions of coded instructions on the DNA strands of which they are constructed.  The chromosomes are duplicated when new cells are produced so that each new cell carries the same set of instructions as all others.  The two exceptions are the reproductive cells (spermatozoa and ova), which, instead of being diploid (two stranded) have only one DNA strand (haploid).   When the sperm fertilizes the egg (ovum) the individual (haploid) strands of DNA are united, producing an entirely new diploid individual related to,  but distinct from, the two source cells.  The new life can literally be said to be half from the mother and half from the father.