Three Billion Letters, One Unrepeatable You

In 2003, scientists at the National Institutes of Health completed the Human Genome Project — thirteen years of painstaking work to map every strand of human DNA. What they found staggered even the researchers. Your body carries roughly three billion base pairs of genetic code, enough information to fill two hundred volumes the size of a Manhattan phone book. And yet, if you uncoiled all the DNA from just one of your cells, it would stretch about six feet long — packed into a nucleus one-tenth the width of a human hair.…