It takes just one egg and one sperm to initiate the complex process of building a human being. Trillions of cells are eventually copied from a single fertilized egg. |
![](https://webarchive.library.unt.edu/eot2008/20080917180602im_/http://www.nlm.nih.gov/changingthefaceofmedicine/img/spacer.gif) |
Genetic information in the form of deoxyribonucleic acid, or DNA, is duplicated and passed on as cells divide and multiply. View the text-only version |