Navigation Links
X-effect: female chromosome confirmed a prime driver of speciation
Date:10/17/2007

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 chromosomethe female chromosome in most animalsplays 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 influentialand 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 malesfar 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, doesnt 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. Its a bit like cross-referencing two encyclopedias for errors, says Presgraves. In the case of X and Y, however, its like trying to cross-reference an encyclopedia with a pamphlet.

But Presgraves believes its not a simple case of the X chromosome being exposed. He believes theres something special about the X. Somehow, it attracts genes that disrupt the creation of sperm in hybrid malesthe main cause of the hybrids 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 flys 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 chromosomes unusually prominent role in the origin of new species.


'/>"/>

Contact: Jonathan Sherwood
jonathan.sherwood@rochester.edu
585-273-4726
University of Rochester
Source:Eurekalert

Related biology news :

1. Female sex hormones play a vital role in defense against sexually transmitted diseases
2. Mother birds increase progesterone to hatch females
3. Decisions, decisions: Male or female?
4. Female volunteers prepare for a second bedrest
5. Looks matter to female barn swallows
6. Picky female frogs drive evolution of new species in less than 8,000 years
7. Female butterflies go for sparkle -- not size -- when choosing to mate
8. Male elephants woo females with precise chemistry
9. Older female fish prefer imperfect male mates, study finds
10. New study explores beetle species with two forms of females
11. Male rivalry increases when females at most fertile, say researchers
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/11/2017)... MOINES, Iowa , Jan. 11, 2017 ... industry first with the release of its patent-pending calibration ... quickly and reliably perform calibrations, securely upload data logs ... flexibility for the customer. "Fighting drunk driving ... only for the public at large, but also for ...
(Date:1/6/2017)... Calif. , Jan. 5, 2017  Delta ID ... its iris scanning technology for automotive at CES® 2017. ... GNTX ) to demonstrate the use of iris ... identify and authenticate the driver in a car, and ... during the driving experience. Delta ID and ...
(Date:12/22/2016)... 2016  As part of its longstanding mission to improve ... company, recently released its latest children,s book, titled ... on the topics of inheritance and variation of traits that ... in elementary school classrooms in the US. ... Ariana Killoran , whose previous book with 23andMe, ...
Breaking Biology News(10 mins):
(Date:1/18/2017)... ... 2017 , ... Researchers from a new study are stating that if levels of ... cancer treatment, this indicates there is still remaining prostate cancer cells that are more likely ... test has always been an indicator of whether a man’s prostate cancer is growing ...
(Date:1/18/2017)... PA (PRWEB) , ... January 18, 2017 , ... Thirty-six ... in tax credits by the Pennsylvania Department of Community and Economic Development in 2016 ... companies are located in the University City Keystone Innovation Zone and represent the highest ...
(Date:1/18/2017)... 18, 2017 /PRNewswire/ - SQI Diagnostics Inc. (TSX-V: ... company that develops and commercializes proprietary technologies and ... "Company"), today announced that Cameron Prange , ... resigned from its Board of Directors.  Mr. Prange,s ... regulations that have limited both his ability to ...
(Date:1/17/2017)... YORK , Jan. 17, 2017 ... grow at a CAGR of around 7.5% over ... by 2025. Some of the prominent trends that ... growing incidences of diseases & graft transplant surgeries ... on Material the market is categorized into immunomodulatory ...
Breaking Biology Technology: