Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Clues to chromosome crossovers

14.02.2013
Neil Hunter’s laboratory in the UC Davis College of Biological Sciences has placed another piece in the puzzle of how sexual reproduction shuffles genes while making sure sperm and eggs get the right number of chromosomes.
The basis of sexual reproduction is that a fertilized egg gets half its chromosomes from each parent — sperm and eggs each contributing one partner in each pair of chromosomes. We humans have 23 pairs of 46 chromosomes: so our sperm or eggs have 23 chromosomes each.

Before we get to the sex part, though, those sperm and eggs have to be formed from regular body cells that contain twice as many chromosomes. That happens through a specialized type of cell division, meiosis.

During meiosis, the couples in each pair of chromosomes have to, well, couple by “crossing over” with each other. Each chromosome pair must become connected by at least one crossover so that when the couples separate, they are delivered to separate sperm or egg cells.

These crossovers also mean that chromosomes can exchange chunks of DNA with each other, shuffling the genetic deck for the next generation. But if too few crossovers are formed, gametes end up with the wrong number for chromosomes, a situation that can cause infertility, pregnancy miscarriage or chromosomal diseases such as Down Syndrome.

Large-scale studies of human genetics have shown that the number of crossovers formed during meiosis is under genetic control. Moreover, women that make more crossovers tend to have more children. One gene suggested to control crossover numbers in humans, called Rnf212, is the subject of a new study by UC Davis researchers lead by Professor Neil Hunter.

Hunter studies how crossovers form and chromosomes separate at the UC Davis Department of Microbiology & Molecular Genetics and the Comprehensive Cancer Center. In 2009, he was awarded an early career fellowship from the Howard Hughes Medical Institute.

The latest paper from Hunter’s lab, published Feb. 10 in Nature Genetics, shows that Rnf212 is essential for crossing-over in mammalian cells. Crossovers form by a process called homologous recombination, in which chromosomes are first broken and then repaired by coupling with a matching template chromosome. Although hundreds of recombination events are started in each cell, only one or two crossovers will form between any given pair of chromosomes.

“There isn’t a special, predetermined site for a crossover. It can occur just about anywhere along a chromosome. But there has to be at least one and there always is,” Hunter said.

In a series of experiments in mouse cells, graduate student April Reynolds, Hunter and colleagues found that the RNF212 protein defines where crossovers will occur by binding to just one or two recombination sites per chromosome where it triggers the accumulation of the protein machinery that actually carries out the cutting and splicing of DNA.

Mice that lacked the gene for RNF212 were sterile. Mice that had one working copy of the gene were fertile, but on careful examination there were fewer crossovers formed while sperm and eggs were being made than in normal mice, potentially reducing fertility. It’s possible that this might be tied to some causes of infertility in humans.

It remains unclear how each pair of chromosomes always manages to crossover at least once. But Hunter says he is, “convinced that RNF212 holds the key to understanding this unique problem in chromosome biology.”

The full author list of the paper is: April Reynolds, Huanyu Qiao, Ye Yang, Jefferson Chen, Neil Jackson, and Kajal Biswas, all in Hunter’s laboratory at UC Davis; J Kim Holloway, Cornell University; Frédéric Baudat and Bernard de Massy, Centre National de Recherche Scientifique, Montpellier, France; Jeremy Wang, University of Pennsylvania; Christer Höög, Karolinska Institutet, Stockholm, Sweden; Paula Cohen, Cornell University; & Neil Hunter.

The work was supported by NIH and HHMI.

Andy Fell | EurekAlert!
Further information:
http://www.ucdavis.edu

More articles from Life Sciences:

nachricht More genes are active in high-performance maize
19.01.2018 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht How plants see light
19.01.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

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...

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

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>