Genomic archeology reveals early evolution of sex chromosomes

May 17, 2011

A team from Uppsala University, Uppsala, Sweden, is using genomics to shed light on the early evolutionary history of sex chromosomes. The research is published in the April 2011 Eukaryotic Cell.

Among other things, the is a place where the distant past can be investigated. Researchers have used it most notably to trace the relationships among species far more accurately than can be done with conventional methods.
 
in animals are so ancient—in the hundreds of millions of years old--that they retain few traces of the historical events that drove their evolution. But the researchers had found in earlier studies that the mating type chromosomes in the self-fertilizing fungus, Neurospora tetrasperma, which are analogous to X and Y in sexually reproducing organisms, have a region of suppressed recombination that is roughly as recent as the split between chimpanzees and hominins—less than six million years old.
 
Suppressed recombination preserves the genomic landscape, because normally, chromosomes recombine during mating, which shuffles the genes like a deck of cards. But suppressed recombination also interferes with natural selection, by forcing genes to be selected or deselected in packages, like the packages of options on new cars that force you to buy the navigation system, the satellite radio, and the MP3 system if you want the side curtain airbags.
 
The Uppsala researchers’ major discovery is that many preferred codons disappeared from regions of the mating type chromosomes where recombination was suppressed. Codons are the “words” of the genetic code. Different codons code for each of the 20 amino acids used in living systems. They code for amino acids, which are the building blocks of proteins, the molecules that form both most of the structure, and most of the machinery cells. Like words in human language, codons often have synonyms. But “Many organisms studied to date preferentially use a specific set of preferred codons which are believed to promote efficient and accurate protein synthesis,” says corresponding author Hanna Johannesson. Thus, they are known as “preferred codons.”
 
The suppressed recombination the researchers had found earlier in N. tetrasperma is accompanied by the loss of these preferred codons.
 
Beyond this, “Our study furthers the understanding of factors driving mutational changes in genomes, which is a key issue in medical and natural science,” says Johannesson. “For example, the onset of mutations, and the ability, or inability of organisms to eliminate them from their genome underlie key processes such as the onset of diseases in animals, and the rate of species extinctions. Our study advances the understanding of when and how young regions of suppressed recombination in sex regulating accumulate mutations, and why evolution may fail to remove these harmful changes in an efficient manner.”

Explore further: Two-armed control of ATR, a master regulator of the DNA damage checkpoint

More information: C. A. Whittle, et al., 2011.  Degeneration in Codon Usage within the Region of Suppressed Recombination in the Mating-Type Chromosomes of Neurospora tetrasperma. Eukaryotic Cell.  10: 594-603

Provided by American Society for Microbiology

3 /5 (1 vote)

Related Stories

Fungi can tell us about the origin of sex chromosomes

Mar 17, 2008

Fungi do not have sexes, just so-called mating types. A new study being published today in the prestigious journal PLoS shows that there are great similarities between the parts of DNA that determine the sex of plants and an ...

Sex and the single chromosome

Nov 26, 2010

Is there value to sex? For higher organisms, absolutely. Animals, plants and fungi that reproduce only by cloning are scarce as hen's teeth, suggesting the gene shuffling of sex pays handsome dividends.

Study maps hotspots of genetic rearrangement

Apr 05, 2011

Researchers have zoomed in on mouse chromosomes to map hotspots of genetic recombination — sites where DNA breaks and reforms to shuffle genes. The findings of the scientists at the National Institutes ...

Recommended for you

Japanese scientist resigns over stem cell scandal

Dec 19, 2014

A researcher embroiled in a fabrication scandal that has rocked Japan's scientific establishment said Friday she would resign after failing to reproduce results of what was once billed as a ground-breaking study on ...

'Hairclip' protein mechanism explained

Dec 18, 2014

Research led by the Teichmann group on the Wellcome Genome Campus has identified a fundamental mechanism for controlling protein function. Published in the journal Science, the discovery has wide-ranging implications for bi ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.