Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Harmful Genes
Name: Dan DeVito
Status: Student
Age: 18
Location: N/A
Country: N/A
Date: March 2004

Why are most harmful genes recessive? What would happen if they were dominant?

Why are most harmful genes recessive? What would happen if they were dominant?

The most harmful genes are recessive because that is really the way they can survive. If a harmful gene were dominate, the individual likely won't live long enough to have offspring (although modern medicine is changing this situation). That's why dominate harmful genes are so rare.

(Look up how Sickle Cell Aenima has survived if you want want a really cool harmful genetic disorder that has a very big advantage to some of those who carry it).

Recessive genes are pretty cool because they are able to hide within a population, without falling out of a gene pool. (It's important to keep in mind that recessive genes are as likely to fall out of a gene pool as dominate genes). For instance - my dad has blue eyes, and my mom has brown eyes. I have brown eyes but I am carrying the blue eye gene - but it doesn't show up. I am as likely to pass on my dominate brown eyed gene as my blue eyed gene - thus the survival of either is 50/50. The same goes for harmful genes. They are able to survive in the gene pool and are able to be passed on because they, like my dad's blue eyed gene, are able to hide. Unless I marry someone who also has a blue eyed gene (ha! - if only I can find a sucker) then there is no way my blue eyed gene could show up. Harmful recessive genes work the same way.

It's for this reason that testing oneself of genetic disorders before having babies isn't a bad idea, especially if harmful genetic diseases have shown up in your family. Two individuals could be carring a very nasty recessive gene and have NO CLUE it's in the genetic make-up - but could easily show up in their children. Good mechanism for hinding and survival, don't you think?

Hope that helps!!

Take care.
Susie Sample B.S.B.M.E.

Click here to return to the Molecular Biology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory