Chromosomes are distinct dense bodies found in the nucleus of cells, composed of protein and DNA. containing genetic information in the form of linear sequences of oases (A,T,C,G). The DNA in an individual chromosome is one, long molecule which is highly coiled and condensed (figure l).The total number of bases in all the chromosomes of a human cell is approximately six billion and individual chromosomes range from 50 to 250 million bases. The DNA sequence for a single trait is called a gene. Each chromosome contains a few thousand genes, which range in si?e from a few thousand bases up to 2 million bases.