DNA is ideal for information storage because it is a very stable molecule and will therefore be unchanged in a person’s descendants, except for occasional mutations. But, because mutations do occur and can sometimes be harmful, the need to have at least two different copies for each gene led to the need for organisms to generally have two sexes, and by mating they contribute these genes to the offspring, so that there would be a greater likelihood that one gene from each such pair would be unchanged and still function normally. Therefore, the process of sex arose simply to ensure this combining of DNAs in any new offspring. Even bacteria exchange DNA. A brief discussion of how DNA was discovered and the history of molecular biology. The process and consequences of DNA replication. To accomplish the complete replication of a human genome requires many origins for replication at the same time. Depiction and description of a mammalian gene with control elements and promoter sequences, TATA box, as well as exons and introns. New mRNAs are protected by a 5′ cap and a 3′ poly-A tail. Description of DNA sequencing methods. Description of DNA fingerprinting using RFLP (recombinant fragment length polymorphism) or snp (single nucleotide polymorphism), or STRs (short tandem repeats). Description of electrophoresis for separating proteins or nucleic acid molecules. Description of DNA repair. Discussion of mutation rates. Long-lived animals have better DNA repair, and larger animals have longer lifespans. The use of methylation to silence genes when they do not need to be active, and enzymes that can reverse that.