Human DNA is one of the main targets of genetic engineering research that for simplifying understanding it they classify different functions and structures of DNA from gene to chromosome and all other definitions.

The diploid human genome is thus composed of 46 DNA molecules of 24 distinct types. Because human chromosomes exist in pairs that are almost identical, only 3 billion nucleotide pairs (the haploid genome) need to be sequenced to gain complete information concerning a representative human genome.