Elder scratched his chin again. “Well, where to begin? Maybe a quick, simplified overview. Every cell in the human body contains a command center of sorts, a nucleus. You probably remember that from—’ “I don’t think blood cells have nuclei,” Anne interrupted. Elder nodded hastily. “That’s right. Blood cells don’t. But most others do. Anyway, inside each nucleus there are chromosomes-little wormlike clusters of specialized molecules made up of deoxyribonucleic acid, or DNA. We have forty-six of these chromosomes altogether. Everybody’s are the same, except males have an X and a Y chromosome, females two X’s. These forty-six chromosomes carry all the human genes. And we still haven’t found them all. The latest count puts the number at over 150,000. And these genes are not separate entities—they’re really just special stretches of DNA code on the chromosomes, each assigned to perform a specific function. No, correct that—each carrying its own set of directions for how to assemble and operate a specific part of the human body.
