Featured Research

from universities, journals, and other organizations

Cataloging The Structural Variations In Human Genetics

Date:
May 10, 2007
Source:
Howard Hughes Medical Institute
Summary:
Using DNA from 62 people who were studied as part of the International HapMap Project, researchers are now looking for structural variations in DNA that may amount to as much as 5 to 10 percent of the human genome. Researchers involved in the project say the amount of work is like doing 62 additional human genome projects.

Computer-generated image of DNA double helix.
Credit: National Human Genome Research Institute

A major new effort to uncover the medium- and large-scale genetic differences between humans may soon reveal DNA sequences that contribute to a wide range of diseases, according to a paper by Howard Hughes Medical Institute investigator Evan Eichler and 17 colleagues published in the May 10, 2007, Nature. The undertaking will help researchers identify structural variations in DNA sequences, which Eichler says amount to as much as five to ten percent of the human genome.

Related Articles


Past studies of human genetic differences usually have focused on the individual “letters” or bases of a DNA sequence. But the genetic differences between humans amount to more than simple spelling errors. “Structural changes — insertions, duplications, deletions, and inversions of DNA — are extremely common in the human population,” says Eichler. “In fact, more bases are involved in structural changes in the genome than are involved in single-base-pair changes.”

In some cases, individual genes appear in multiple copies because of duplications of DNA segments. In other cases, segments of DNA appear in some people but not others, which means that the “reference” human genome produced by the Human Genome Project is incomplete. “We're finding new sequence in the human genome that is not in the reference sequence,” Eichler says.

These structural changes can influence both disease susceptibility and the normal functioning and appearance of the body. Color-blindness, increased risk of prostate cancer, and susceptibility to some forms of cardiovascular disease result from deletions of particular genes or parts of genes. Extra copies of a gene known as CC3L1 reduce a person's susceptibility to HIV infection and progression to AIDS. Lower than normal quantities of other genes can lead to intestinal or kidney diseases.

Variation in the number of genes or in gene regulation caused by structural rearrangements may also contribute to more common diseases. “The million dollar question is what is the genetic basis of diseases like diabetes, hypertension, and high cholesterol levels?” says Eichler. “ We know there is a genetic factor, but what is the role of single base pair changes versus structural changes?”

The project Eichler and his colleagues describe in their paper will help answer this question. Using DNA from 62 people who were studied as part of the International HapMap Project, they are creating bacterial “libraries” of DNA segments for each person. The ends of the segments are then sequenced to uncover evidence of structural variation. Whenever such evidence is found, the entire DNA segment is sequenced to catalog all of the genetic differences between the segment and the reference sequence.

The result, says Eichler, will be a tool that geneticists can use to associate structural variation with particular diseases. “It might be that if I have an extra copy of gene A, my threshold for disease X may be higher or lower.” Geneticists will then be able to test, or genotype, large numbers of individuals who have a particular disease to look for structural variants that they have in common. If a given variant is contributing to a disease, it will occur at a higher frequency in people with the disease.

Knowing about structural variation in the human genome will also allow geneticists to analyze single-base-pair changes more effectively, according to Aravinda Chakravarti, a geneticist at The Johns Hopkins University School of Medicine who was not a coauthor of the paper. “We have to look at structural variants from a different perspective, because they are adding or subtracting something from the genome,” Chakravarti says. By understanding the patterns of both structural variants and single-base-pair changes in the population, “we'll learn a lot.” To use both kinds of information in tandem, Eichler and his colleagues plan to incorporate the structural information they gather into existing databases on single-base-pair changes.

The project, which is being funded by the National Human Genome Research Institute at the National Institutes of Health, is difficult and expensive, Eichler admits. “It's a lot of work, because it's essentially doing 62 additional human genome projects,” he says. “Having been involved in the first one, I swore I would never do it again. But in this case we're looking at the coolest parts of the genome.”


Story Source:

The above story is based on materials provided by Howard Hughes Medical Institute. Note: Materials may be edited for content and length.


Cite This Page:

Howard Hughes Medical Institute. "Cataloging The Structural Variations In Human Genetics." ScienceDaily. ScienceDaily, 10 May 2007. <www.sciencedaily.com/releases/2007/05/070509161020.htm>.
Howard Hughes Medical Institute. (2007, May 10). Cataloging The Structural Variations In Human Genetics. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2007/05/070509161020.htm
Howard Hughes Medical Institute. "Cataloging The Structural Variations In Human Genetics." ScienceDaily. www.sciencedaily.com/releases/2007/05/070509161020.htm (accessed October 25, 2014).

Share This



More Health & Medicine News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Texas Nurse Nina Pham Cured of Ebola

Texas Nurse Nina Pham Cured of Ebola

AFP (Oct. 25, 2014) — An American nurse who contracted Ebola while caring for a Liberian patient in Texas has been declared free of the virus and will leave the hospital. Duration: 01:01 Video provided by AFP
Powered by NewsLook.com
Toxin-Packed Stem Cells Used To Kill Cancer

Toxin-Packed Stem Cells Used To Kill Cancer

Newsy (Oct. 25, 2014) — A Harvard University Research Team created genetically engineered stem cells that are able to kill cancer cells, while leaving other cells unharmed. Video provided by Newsy
Powered by NewsLook.com
IKEA Desk Converts From Standing to Sitting With One Button

IKEA Desk Converts From Standing to Sitting With One Button

Buzz60 (Oct. 24, 2014) — IKEA is out with a new convertible desk that can convert from a sitting desk to a standing one with just the push of a button. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com
Ebola Protective Suits Being Made in China

Ebola Protective Suits Being Made in China

AFP (Oct. 24, 2014) — A factory in China is busy making Ebola protective suits for healthcare workers and others fighting the spread of the virus. Duration: 00:38 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins