– What “writes” the information on DNA? And how does it adquire that information?
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Outside of some specific instances, DNA isn’t written to- it’s more like ROM. Mutations can change individual base pairs or rearrange sequences, and certain viruses can inject new DNA into an existing genome, but there’s not much in the way of a mechanism that writes DNA.
So where did all your DNA come from? Well, mutations and viruses primarily- mutations create genetic variation and natural selection preserves useful variations. A large portion of your DNA is slightly mutated copies of other genes in your genome. The process of meiosis, which creates sex cells, involves swapping genes between neighboring chromosomes. This occasionally introduces errors, like a chromosome picking up a second copy of a gene it already has, or even an entirely different version. These types of mutations increase the size of the genome over billions of years, while natural selection pares down useless or harmful effects.
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