Health and Medical News and Resources

General interest items edited by Janice Flahiff

How many genomes do you have? | SmartPlanet

How many genomes do you have? | SmartPlanet.

By  | November 29, 2011, 3:00 AM PST

The era of personal genomics is fast approaching, as headlines constantly remind us. With the cost of sequencing someone’s DNA rapidly falling toward just $1,000 (or less), it seems all but inevitable that soon we and our physicians will use that information to guide our health decisions.

 

 

454 Life Sciences gene sequencing machines. (Credit: Jon Callas, via Flickr)454 Life Sciences gene sequencing machines. (Credit: Jon Callas, via Flickr)

 

But here’s an inconvenient biological truth that the triumphant talk about personal genomics sometimes skirts: we don’t each have just one genome. Yes, one may stand out most prominently for each of us, but we have others. And biology is still sorting out how much our health may depend on learning to pay attention to those we normally overlook.

 

All the cells in an organism like a human being certainly seem as though they should have the same genome. A fertilized egg divides repeatedly to give rise to the body’s cells, passing along the same set of chromosomes to every one of its cellular progeny. A few exceptional tissues might deviate from that rule — for example, red blood cells entirely discard the nucleus holding their genes, and the white blood cells called B lymphocytes scramble part of their DNA so that they can make an almost infinite number of different antibodies. But fundamentally, all the cells in the skin, the liver, the brain, the muscles and other tissues ought to share the same genome.

Or so it was thought. Yet exceptions to the rule keep cropping up, and they may help to explain some of the variation seen in tissues like the brain.

Variation on the brain

The hundred billion neurons in the human brain obviously differ from one another in their interconnections and in the specific neurochemical messenger molecules that they secrete. But a more subtle difference that has come to light over the past decade, largely thanks to the work of Michael J. McConnell and his colleagues at the Salk Institute for Biological Studies in La Jolla, Calif., resides in the DNA. They have shown extensive variation in the genomes of individual neurons, a condition called aneuploidy. The neurons have deleted, duplicated, and rearranged portions of their chromosomes, such that no two have exactly the same DNA sequence anymore…..

 

November 30, 2011 - Posted by | Medical and Health Research News | , , ,

No comments yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: