New Delhi: A large international study jointly led by Uppsala University in Sweden and the Broad Institute in the US, that analysed the genomes of 240 mammal species, has revealed which regions have important functions in mammals, which genetic changes have led to specific characteristics in different species and which mutations can cause disease.

More than 30 research teams surveyed and analysed the genomes of 240 mammal species and published their results in 11 articles in the journal Science, showing how the genomes of humans and other mammals have developed in the course of evolution.

"In combination, the 11 articles provide an enormous amount of information about the function and development of mammalian genomes. Moreover, we have produced data that can be used for studies of evolution and medical research for many years to come," said Kerstin Lindblad-Toh, Professor of Comparative Genomics at Uppsala University. The human genome contains approximately 20,000 genes that constitute the code for manufacturing all the proteins in the body. The genome also contains instructions that direct where, when and how much of the proteins are produced.

These parts of the genome, which are called regulatory elements, are much more difficult to identify than the parts that give rise to proteins. However, studying a great many mammals' genomes makes it possible to figure out which parts of the genome are functionally important.

The researchers identified regions of the human genome with previously uncharacterised function. These regions are likely regulatory elements and are significant for the correct functioning of the genome. Mutations in these can play an important role in the origin of diseases or in the distinctive features of mammal species.

They identified more than three million important regulatory elements in the human genome, about half of which were previously unknown. They were also able to ascertain that at least 10 per cent of the genome is functional, 10 times as much as the approximately one per cent that codes for proteins.

The 240 different mammals in the study vary widely in their characteristics, such as the acuteness of their sense of smell or the size of their brain. The researchers were able to find regions in the genomes that lead to some species having a superior sense of smell or to certain species hibernating.

"It's exciting to now have a picture of which mutations have steered the development of specific traits in these widely divergent mammals," says Matthew Christmas, researcher and co-first author of one of the articles focusing on the function of the genome. One of the studies shows that mammals had begun to change and diverge before the Earth was hit by the asteroid that killed the dinosaurs, approximately 65 million years ago.

The researchers also pinpointed parts of the genome linked to a few exceptional traits in the mammalian world, such as extraordinary brain size, superior sense of smell, and the ability to hibernate during the winter.

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