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publicado em 29/05/2011 às 15h00:00
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Archaeology genomics reveals the early evolution of sex chromosomes

Researchers are using genomics to shed light on the evolutionary history of sex chromosomes

 
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P esearchers are using genetic archeology in the genome to investigate the relationship between the sexual species s. Sex chromosomes in animals are so old - hundreds of millions of years - q ue retain only a few vestiges of the historical events that led to its evolution. But the researchers found that the types of crossing the chromosomes in the fungus Neurospora tetrasperma self-fertilized, similar to the X and Y in sexually reproducing organisms have a region of repressed recombination that is historically as recent as the split between chimps and hominids, which occurred less than six million years.

The suppressed recombination preserves the landscape of the genome because, normally, the chromosomes recombine during the crossing, which shuffles genes. But the suppressed recombination interferes with natural selection, by requiring genes to be selected or not in packages, and package options to new cars that force you to buy the navigation system, satellite radio and MP3 system, if want the side airbags.

The most important finding of researchers from Uppsala is that many codons have disappeared from the type of crossover regions of the chromosomes where recombination was suppressed. Codons are the "words" of the genetic code. Different codons representing each of the 20 amino acids used in living systems. They represent amino acids that are the building blocks of proteins, the molecules that make up the majority of both the structure as the cellular machinery. Since words in human language, often synonymous codons have. But many organisms studied to date, preferably using a specific set of codons which we believe to promote the efficient and accurate protein synthesis, Hanna Johannesson said. Thus, they are known as "preferential codons".

The suppressed recombination that researchers had previously found in N. tetrasperma is accompanied by loss of codon bias.

In addition, the study reinforces the understanding of the factors driving the changes in the genomes, which is a central issue in medical and natural sciences. For example, the appearance of mutations as well as the ability or inability of agencies to clear them of key processes underlying genome, as the onset of diseases in animals and the rate of species extinction. Our study advances the understanding of when and how young regions of suppressed recombination in the sex chromosomes regulators accumulate mutations and that evolution can fail to remove these harmful changes in an efficient manner, "says Johannesson.

France

Source: Isaude.net
   Palavras-chave:   X chromosome    Genome evolution    Natural selection    Amino acids    Genomic recombination   
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