DNA – aka deoxyribonucleic acid is a chain molecule made up of a sequence of molecular components that exists in nearly all organisms. The components are known as chemical bases which act as a code of instructions for making an entire living being to develop and survive. DNA is stored in the nucleus of every cell tightly coiled into 23 pairs of chromosomes (except blood cells, since they lose their DNA as the mature). We inherit 23 chromosomes from our parents.
DNA is often known to be in a form of a double helix made of two strands of sugar and phosphate linked together by a pair of bases, and these bases form long sequence called genes that are coded instructions to build proteins. When a cell needs to duplicate or make a protein, the helix splits itself into two halves so that a copy of the gene can be made. The bases are Adenine (A), Thymine (T), Guanine (G) and Cytosine (C) – they always form with the same pairs (A-T, G – C) and these pair make up the entire sequence of DNA.
Since genes code the molecules that are essential for life, majority of genes are the same in everyone. However only about 1% have different variations – known as alleles which give unique physical traits like hair or eye color. They could result in more problematic conditions, like hemophilia or cystic fibrosis because alleles come in pairs, one can override the other so that the trail remain hidden.