The August issue of the American scientific journal Genome Research already on the cover encourages you to read an article by a Pole – Marcin von Grotthuss and his two associates. The described research fills the gap in the existing knowledge about the evolution of chromosomes.
The hypothesis of the existence of fragile regions in chromosomes was proposed in 2003 by two scientists from the United States (Glenn Tesler and Pavel Pevzner), but so far no one has managed to present a formal proof of their existence – he told PAP Dr. Marcin von Grotthuss, currently working at the BioInfoBank Institute in Poznań.
The scientist and his team made such proof using a range of computer simulations. It is presented in the article Fragile regions and not functional constraints predominate in shaping gene organization in the genus Drosophila, published in Genome Research.
Our discovery will provide a better understanding of how higher organisms, including mammals, have evolved at the level of entire chromosomes. This knowledge will also make it possible to understand the mechanisms of the formation of certain types of cancer, as some of the evolutionary fragile places in the human genome are involved in the formation of cancer cells – the researcher says. He adds that now we understand how the chromosomes as a whole are evolving
Until now, it was assumed that genes evolve grouped into clusters, i.e. functional groups that cannot be disrupted because they would lose this functionality, and the birth of an organism with a disrupted functional cluster would risk either its immediate death or worse development. We proved that only a small part of the clusters (with a total size of 15% of the genome) is protected against disruption. The others are not torn apart not because their genes are functionally related to each other, but because the clusters do not have fragile spots, says Dr. von Grotthuss.
A cluster is a group of genes arranged close to each other on one chromosome, which, for example, code for the same protein or similar proteins. Due to the fact that populations derived from one ancestor have similar types of gene clusters, they can be used to check the evolutionary origin of given organisms.
Dr. von Grotthuss worked on his ID for about 4 years. This discovery would not be possible without the financial support of the Foundation for Polish Science, which financed my research internship at the California University in the United States under the + Columb + scholarship – he emphasizes.
The work began by finding conserved clusters, that is, clusters with the same genes arranged in the same order in 9 species of Drosophila. Then, using an appropriate computer program, the scientists reconstructed the order of these clusters in the last ancestor for all studied flies and estimated that there were 3 flies. gene rearrangements that differentiated the genomes of the studied flies.
The next stages of the experiment consisted in checking the role of cold and brittle places in the evolution of chromosomes of 9 species of Drosophila fly, which lived only 30 days, where – as assumed – cold places are areas that cannot be torn apart, and fragile places – sensitive to these tears.
At one point, we concluded that the cold regions could not explain why we have fragile spots on the chromosomes, describes Dr. von Grotthuss, and that if you run out of fragile spots, you can’t get the cold regions. In turn, when in a computer simulation we have a lot of fragile points and a small number of cold spots, such a simulation will recreate the genomes of 9 Drosophila flies that occur in nature.
The scientist, using a series of graphs and charts, proves that chromosomes break in fragile places, and seemingly functionally connected genes in clusters can be separated if fragile points appear in a given cluster.
This was a big surprise to us as we were taught that gene clusters do not break apart. Some scientists even believed that an organism with a disrupted conserved cluster of many genes had no right to be born. However, as it turns out, they were wrong, which we have just proved. In addition, at the University of California in the USA (University of California), experiments are carried out on fruit flies and there is a break in such a large, conserved cluster of genes. After such an operation, flies not only reproduce, but also develop well, describes Dr. von Grotthuss. (PAP)