Bioinformatics used new computer technologies to study the structure of chromosomes and tested them on marigold butterflies. So it was possible to see unusual traces of rapid chromosomal evolution: some chromosomes merged together, and some of their sections turned 180 degrees. It was previously impossible to assume such large changes, because even in the best microscope, the chromosomes of butterflies are visible as small black balls without a pronounced internal structure. Such a bioinformatic approach can be used to detect human chromosomal diseases and be less labor-intensive compared to conventional methods. The research is supported by a grant from the Russian Science Foundation. The results are published in the journal Genes.

Thousands of researchers around the world are studying chromosomes. For biologists, this is a way to learn the laws of genetics and evolution, because there are genes in chromosomes, and genes carry information necessary for the development of organisms. For doctors, this is one of the ways to diagnose diseases, many of which arise due to a violation of the structure and number of chromosomes. For example, Wolf-Hirshhorn syndrome can be accurately determined only after the birth of a child — this is a rare genetic disease that occurs due to the loss of a small section of one of the chromosomes and leads to multiple developmental disorders. Many other chromosomal changes occur in different forms of cancer. Therefore, it is very important for scientists to be able to identify chromosomal rearrangements and do it as accurately as possible. Until now, such studies have been carried out — and are still being carried out — using a microscope, but this approach has serious limitations: many rearrangements are so small that they cannot be detected.

In recent years, scientists from different countries have begun to develop approaches to detecting chromosomal rearrangements using computer technology. The staff of the Zoological Institute of the Russian Academy of Sciences (St. Petersburg) and the University of Ljubljana (Slovenia) tested one of the algorithms that can be used for fine analysis of the structure of chromosomes. As an object, they took butterflies from the family of marigolds (satyrids), because earlier, when studying them, they learned that the chromosome sets of almost all species are the same. The authors analyzed information about the genomes of butterflies from the international genetic bank. For each pair of marigold species, scientists took thousands of genes, which they put together and plotted on graphs according to their position on chromosomes. This made it possible to identify those parts of the genome in which the structure has changed during evolution.

The analysis showed that satirid butterflies have experienced a rapid chromosomal evolution. In some species, this happened due to the fusion of chromosomes, when two smaller chromosomes join into one. In other species, this happened due to the accumulation of multiple inversions — 180-degree reversals of chromosome fragments. Such changes are important for preserving the ecological adaptations that species acquire during evolution and speciation.

"Our analysis showed that the genomic evolution of the studied insects was much more rapid than expected. In the future, we want to study in detail their telomeres — the end sections of chromosomes that are important for preserving the integrity of the genome. We hope that this will help us to understand the causes and mechanisms that led to the transformation of chromosomes," said Vladimir Lukhtanov, head of the project supported by the RNF grant, Doctor of Biological Sciences, Chief Researcher of the Zoological Institute of the Russian Academy of Sciences.

Information provided by the press service of the Russian Science Foundation

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