Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Genetic Conflict in Fish Led to Evolution of New Sex Chromosomes

05.10.2009
University of Maryland biologists have genetically mapped the sex chromosomes of several species of cichlid (pronounced "sick-lid") fish from Lake Malawi, East Africa, and identified a mechanism by which new sex chromosomes may evolve.

In research published in the journal Science (October 1, 2009), Professor Thomas D. Kocher, Department of Biology, College of Chemical and Life Sciences; Reade Roberts, post-doctoral associate; and Jennifer Ser, research associate, describe the genetic basis for two co-existing systems of sexual determination in cichlid fish from Lake Malawi.

In nearly all mammals, the gene that determines the sex of offspring is located on the Y chromosome, which is much smaller than the X chromosome. But in many other animal groups, the genetic mechanism of sex determination evolves quite rapidly, and the differences between sex chromosomes are harder to observe. Even sister species of fish may have entirely different sex determination systems. How and why the genetic mechanisms for such an ancient developmental distinction continue to evolve has remained a mystery. The thousands of closely related cichlid fishes in the lakes of East Africa turn out to be an excellent model system for understanding how the mechanisms of how sex determination evolve.

The East African cichlid fishes that inhabit Lakes Malawi, Tanganyika, and Victoria are known for their sexually distinct appearance – the males are generally conspicuous and brightly colored, making them more attractive to females, while the females are drab and brown, making them inconspicuous to predators. One exception to the uniformly brown pigmentation among female cichlids is the "orange blotch" pattern, which appears in some female cichlids that live in rocky areas of Lake Malawi. "We believe that the orange blotch color pattern emerged as a new mutation in females and has a selective advantage in providing an alternative form of camouflage," says Dr. Kocher, who has been leading research to identify the genetic basis for phenotypic differences in cichlids for the past 20 years, and who made the first crosses to map the gene responsible for this color pattern in 1993.

Depending on the surrounding natural background, this color pattern can help disguise female fish and help them avoid predation. However males who express this phenotype lack the species-specific color patterns used by females to select their mates. "This phenotype creates a sexual conflict because the allele is favored in females but not favored in males," explains Dr. Roberts, who fine mapped the gene. "In 'survival of the fittest,' the genes underlying a beneficial trait will increase in frequency, but this is an odd case where the trait is really good for females but really bad for males."

Using genomic techniques, Roberts identified the gene (pax7) that is responsible for this difference in color pattern. He found that the orange blotch (OB) allele that produces the variable pigmentation in females was dominant over the "brown barred" (BB) allele (that produces the more common brown pigmentation) and that it was located very near a female sex determiner (W). The genetic conflict that started over color was resolved by a new mutation that took over the sex determining function, and ensured that nearly all orange blotch fish are female.

"This study marries two evolutionary mysteries: the incredible diversity of fish in the lakes of East Africa and the genetic basis of sex determination," says Sam Scheiner, program director in the National Science Foundation (NSF)'s Division of Environmental Biology, which funded the research. "This study shows how simple genetic changes can lead to enormous biological diversity."

Kelly Blake | Newswise Science News
Further information:
http://www.umd.edu

More articles from Life Sciences:

nachricht Polymers Based on Boron?
18.01.2018 | Julius-Maximilians-Universität Würzburg

nachricht Bioengineered soft microfibers improve T-cell production
18.01.2018 | Columbia University School of Engineering and Applied Science

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Novel chip-based gene expression tool analyzes RNA quickly and accurately

18.01.2018 | Medical Engineering

Scientists on the road to discovering impact of urban road dust

18.01.2018 | Ecology, The Environment and Conservation

Gran Chaco: Biodiversity at High Risk

17.01.2018 | Ecology, The Environment and Conservation

VideoLinks
B2B-VideoLinks
More VideoLinks >>>