James Watson and Francis Crick determined the structure of DNA in the early 1950s. Together they set out to determine the structure of DNA and to build a
model that would explain how DNA, the genetic material, can very from species to species and even from individual to individual. They also discovered haw
DNA replicates (makes copy of itself) so that daughter cells receive an identical copy.

    Watson and Crick built an actual model of DNA out of wire and tin.  This double-helix model allows differences in DNA structure between species because
the base pairs can be in any order.  Also, the model suggests that complementary base pairing plays a role in the replication of DNA.
    When the body grows or heals itself, cells divide.  Each new cell requires an exact copy of the DNA contained in the chromosomes.  Each original strand
serves as a template for the formation of a complementary new strand.  This replication results in two DNA helices that are identical to each other and to the
original molecule.

    “A gene is a segment of DNA found on a chromosome that specifies the amino acid sequence of a polypeptide; sometimes either a single polypeptide or
multiple polypeptides from proteins. In genes DNA stores the information necessary for forming polypeptides in the form of a nucleotide code” .  

    The general principle of producing a GMO is to add new genetic material into an organism's genome.  This is called genetic engineering and was made
possible through the discovery of DNA and the creation of the first recombinant bacteria in 1973 .

    Genetic modification involves the insertion or deletion of genes.  When genes are inserted, they usually come from a different species, which is a form of
horizontal  gene transfer.  In nature this can occur when exogenous DNA penetrates the cell membrane for any reason.  To do this artificially may require
attaching the genes to a virus or just physically inserting the extra DNA into the nucleus of the intended host with a very small syringe, or with very small
particles fired from a gene gun.
    This great scientific achievement could be used for the service of human race but the words of President D. D. Eisenhower are becoming prophetic.  He says
this; “Yet in holding scientific research and discovery in respect, as we should, we must be alert to the equal and opposite danger that public policy could itself
become the captive of a scientific-technological elite” . (1961)