Through the 1960s up to the 1990s scientists learned how to read DNA's sequence of bases, first by handfuls, then faster and faster. Ray Wu learned to determine the order of a dozen or so bases in the late 1960s. The mid-70's brought Fred Sanger and Alan Coulson's "plus and minus" method, and the first viral DNA sequenced. We then talk of Maxam and Gilbert's method, Kary Mullis' polymerase chain reaction, and Alex Jeffrey's discovery of repetitive sequences. Semi-automatic sequencing arrived in the mid-1980s, and then the Human Genome Project was planned and begun by 1990.