What is functional screening in molecular biology and how is it useful in discovering new genes?

Answer 1

First off, the genes are not new. They've been around for years, we're just trying to figure out what they are.

So, suppose you're looking for the gene that gives people nipples. How do you know, out of the billions and billions of genes people have, which one codes for nipples?

Well, first, you look for someone who is born without nipples. Presumably, someone born without nipples either is missing the nipple gene, or has a nipple gene that is all messed up.

Now, you can scan the DNA of the person without nipples, and see what's so different in their DNA. Eventually, you'll find a spot or two that's pretty unusual, and you can then guess that one of these weird spots is probably the nipple gene.

If this particular part of the DNA sequence is similar in humans and lab rats, you can then fiddle with lab rat DNA in the spots that the no-nipple people have differences, and eventually you should come up with rats that have no nipples, or really weird nipples, and TA DA! You've used functional screening (by screening out a normally functional gene) to determine where the nipple gene is.