See these two wonderful men here?
Their names are James Watson and Francis Crick, and they are credited as discovering the structure of DNA. They basically explained the nucleotide structure, complementary base pairing mechanism, and hence replication processes.
“Some day a child is going to sue it’s parents for being born. They will say, my life is so awful with these terrible genetic defects and you just callously didn’t find out.” -James Watson on the question of genetic screening of foetuses (1997)
“Almost all aspects of life are engineered at the molecular level, and without understanding molecules we can only have a very sketchy idea about life itself.” -Francis Crick (1998)