Navigation Links
Clues to chromosome crossovers
Date:2/13/2013

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.

Chromosome pairs entwined during meiosis. Green spots show the location of RNF212. (Neil Hunter/UC Davis)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."


'/>"/>

Contact: Andy Fell
ahfell@ucdavis.edu
530-752-4533
University of California - Davis
Source:Eurekalert  

Related biology news :

1. Researchers look to relatives for clues in quest to develop sources of bioenergy
2. Relative reference: Foxtail millet offers clues for assembling the switchgrass genome
3. Higher pain tolerance in athletes may hold clues for pain management
4. Clues to nervous system evolution found in nerve-less sponge
5. Preserved frogs hold clues to deadly pathogen
6. Remote Siberian lake holds clues to Arctic -- and Antarctic -- climate change
7. Highlighting molecular clues to the link between childhood maltreatment and later suicide
8. Hunting for autisms chemical clues
9. Salt cress genome yields new clues to salt tolerance
10. Gecko feet hold clues to creating bandages that stick when wet
11. A mechanism providing clues for research into pancreatic diabetes is described
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Clues to chromosome crossovers
(Date:3/22/2016)... , March 22, 2016 ... report "Electronic Sensors Market for Consumer Industry by Type ... Others), Application (Communication & IT, Entertainment, Home ... Global Forecast to 2022", published by MarketsandMarkets, ... expected to reach USD 26.76 Billion by ...
(Date:3/17/2016)... 17, 2016 ABI Research, the leader ... global biometrics market will reach more than $30 ... from 2015. Consumer electronics, particularly smartphones, continue to ... anticipated to reach two billion shipments by 2021 ... Pavlakis , Research Analyst at ABI Research. "Surveillance ...
(Date:3/14/2016)... March 14, 2016 http://www.apimages.com ... --> - Renvoi : image disponible via ... --> --> DERMALOG, le ... de nouveaux lecteurs d,empreintes digitales pour l,enregistrement des ... sera utilisé pour produire des cartes d,identité aux ...
Breaking Biology News(10 mins):
(Date:5/18/2016)... ... 18, 2016 , ... The Academy of Model Aeronautics has been helping graduating ... a total of $1 million in awarded scholarships. , The AMA is happy to ... across the nation has helped bring the total of AMA scholarships that have been ...
(Date:5/17/2016)... -- Haselmeier announces the launch by Merck ... EMA, the European Medicines Agency. Originally launched in 2011 ... new pen version includes enhancements to further improve the ... patients during use. Its enhanced design has ... with a larger display window that improves the readability ...
(Date:5/17/2016)... Arabia (PRWEB) , ... May 17, 2016 , ... ... biopharmaceutical industry, and BioSmartSA, a healthcare consultancy based in Saudi Arabia, have formed ... diagnostic services to healthcare providers in the Kingdom of Saudi Arabia (KSA). ...
(Date:5/17/2016)... York, NY (PRWEB) , ... May 17, 2016 , ... ... Month, buildings, bridges, and monuments across the globe will show their support in the ... NF. , Neurofibromatosis, NF, is a genetic disorder that causes tumors to grow ...
Breaking Biology Technology: