Hi

DNA or deoxyribonucleic acid is a molecule composed of two polynucleotide chain coiling each other in a double helix structure.  They are the carriers of genetic instructions and helps in passing the traits of their parents to their offsprings.

DNA are contains monomeric units called nucleotides and each nucleotide contains 4 nitrogenous bases namely cytosine,guanine, adenine or thymine along with sugar( deoxyribose) and a phosphate group

DNA has three main functions

Passing of genetic information from parents to offspring through genes contained in the DNA

Immunological properties of the body also comes from DNA

And the structural characteristics of a species is also controlled by DNA

Hope this helps