Featured Research

from universities, journals, and other organizations

X-effect: Female Chromosome Confirmed A Prime Driver Of Speciation

Date:
October 19, 2007
Source:
University of Rochester
Summary:
Researchers believe they have just confirmed a controversial theory of evolution. The X chromosome is a strikingly powerful force in the origin of new species. Biologists have argued for years whether the X chromosome -- the female chromosome in most animals -- plays a special role in the process of speciation. A new study has confirmed that the X chromosome is indeed heavily influential -- and the reason may be nothing like what biologists expected.

Researchers at the University of Rochester believe they have just confirmed a controversial theory of evolution. The X chromosome is a strikingly powerful force in the origin of new species.

Biologists have argued for years whether the X chromosome—the female chromosome in most animals—plays a special role in the process of speciation. In a new study in the journal PLoS Biology, Daven Presgraves, professor of biology at the University of Rochester, has confirmed that the X chromosome is indeed heavily influential—and the reason may be nothing like what biologists expected.

When one species splits into two, interbreeding between the two daughter species is much more likely to produce infertile hybrids when the species exchange X chromosomes than when they exchange any other chromosomes, says Presgraves. The process, dubbed the "large X-effect," acts as a wedge between the two newly formed species, pushing them onto divergent evolutionary paths.

Over the course of a year, Presgraves and research associate J. P. Masly interbred fruit flies for 15 generations. The team painstakingly substituted individual genes of one fly species with the genes of a closely related species, and tracked which genes caused infertility in hybrids. The Rochester team showed that 60 percent of X-chromosome genes cause infertility in hybrid males—far higher than the 18 percent for all the non-sex chromosomes.

"There is no more debate," says Presgraves. "The large X-effect is real."

But in solving one mystery, the findings give rise to another.

Scientists expect evolutionary changes in DNA to accumulate in random locations across a genome, but Presgraves instead found that most changes causing hybrid infertility cluster inexplicably on the X chromosome.

Presgraves is now looking into why the X is a hotspot for "speciation genes," that prevent genetic exchanges between closely related species.

The traditional notion of the large X-effect is that the X chromosome is simply "exposed," meaning its complement, the Y chromosome, doesn't have the information needed to mask the effects of changes on the X. We inherit a set of chromosomes from each parent with each chromosome acting as a sort of backup for its complement. It's a bit like cross-referencing two encyclopedias for errors, says Presgraves. In the case of X and Y, however, it's like trying to cross-reference an encyclopedia with a pamphlet.

But Presgraves believes it's not a simple case of the X chromosome being exposed. He believes there's something special about the X. Somehow, it attracts genes that disrupt the creation of sperm in hybrid males—the main cause of the hybrid's infertility, he says.

"When I look at this, I think the X is not behaving normally during spermatogenesis (sperm creation)," says Presgraves. "I think it may be that in the production of sperm, when the fly's genome is shut down and compacted to fit into the sperm head, the X is not shutting down and is wrecking the process."

Presgraves is planning new tests to see if the X is, in fact, refusing to shut down when it should.

If the process that controls normal X inactivation during spermatogenesis is particularly susceptible to evolutionary change, says Presgraves, then it may be largely responsible for the X chromosome's unusually prominent role in the origin of new species.


Story Source:

The above story is based on materials provided by University of Rochester. Note: Materials may be edited for content and length.


Cite This Page:

University of Rochester. "X-effect: Female Chromosome Confirmed A Prime Driver Of Speciation." ScienceDaily. ScienceDaily, 19 October 2007. <www.sciencedaily.com/releases/2007/10/071017105417.htm>.
University of Rochester. (2007, October 19). X-effect: Female Chromosome Confirmed A Prime Driver Of Speciation. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2007/10/071017105417.htm
University of Rochester. "X-effect: Female Chromosome Confirmed A Prime Driver Of Speciation." ScienceDaily. www.sciencedaily.com/releases/2007/10/071017105417.htm (accessed October 20, 2014).

Share This



More Plants & Animals News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
Captive Dolphin Gives Birth

Captive Dolphin Gives Birth

Reuters - Light News Video Online (Oct. 20, 2014) SeaWorld in San Diego welcomes a new bottlenose dolphin, the second calf for 13-year-old female, Sadie. Rough Cut. (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Another Study Suggests Viagra Is Good For The Heart

Another Study Suggests Viagra Is Good For The Heart

Newsy (Oct. 20, 2014) An ingredient in erectile-dysfunction medications such as Viagra could improve heart function. Perhaps not surprising, given Viagra's history. Video provided by Newsy
Powered by NewsLook.com
White Rhino's Death In Kenya Means Just 6 Are Left

White Rhino's Death In Kenya Means Just 6 Are Left

Newsy (Oct. 20, 2014) Suni, a rare northern white rhino at Ol Pejeta Conservancy, died Friday. This, as many media have pointed out, leaves people fearing extinction. Video provided by Newsy
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


Plants & Animals

Earth & Climate

Fossils & Ruins

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