Hopkins' zebrafish originated from the Ganges River in India.

Nancy Hopkins is quite attached to her zebrafish. As she tells Alan in the segment "Fishing for Baby Genes," when she wants to relax, she likes to sit in her lab at MIT and just gaze at them. All 150,000.

Thanks to these fish and some ingenious science, Hopkins has discovered several genes directly responsible for creating a baby fish, and more importantly, a baby human. Because our two species share so much DNA - about 90% of it - the genes that are instrumental in building a heart, liver, and much of the rest of our bodies can also be found in these tiny, striped creatures. And, as Hopkins notes, her fish make much more manageable test subjects.

Alan and Hopkins marvel at her fishy brood, and the potential they hold.

In order to zero in on the critical genes, Hopkins and her team begin by injecting a virus into the fish embryos that causes random mutations to occur. If the virus happened to attach itself to a gene responsible for creating a body part, the descendants of that fish will display the deformity. It's a hit and miss process, but so far, thanks to Hopkins patience and her vast stable of fish, the work is paying off.

As she tells Alan, Hopkins hopes one day to help create a master list of all the genes essential to building a human. Need a new heart? Your doctors would need only to consult the list. While it may be far off, the medical potential of Hopkins' research is enormous.

For more on this topic, see the web feature:
Falling in Love with DNA