WHAT IS DNA?
DNA constitutes our genome. It is a string of four chemicals called nucleotides which are joined together by chemical bonds. . These nucleotides comprise four special chemicals, represented by the letters G, A, T, and C. These are the first letters of the chemicals they represent: Guanine, Adenine, Thymine, Cytosine It is not important to remember their names, just the initials: G, A, T, and C. Thus, the three billion nucleotides that make up our genetic material (DNA) consist of just these four nucleotides arranged in a particular order or sequence, for example ATTGCCGGCTTTTAGAGCCGAT. The nucleotides are linked together by a chemical bond and can be perceived as a very long string. An easy way to understand this is to think of DNA as a big necklace made of beads of four different colors: one color for each nucleotide (GATC). As stated earlier, the three billion nucleotides are not present as one long DNA string but are divided into nucleotide chains present in twenty-three chromosomes.