Cover news reporter Yao Zhenjun
On January 7, the cover news reporter learned that recently, Chinese and foreign scientists have worked together to successfully construct the genome map of the common ancestor of all living mammals, including humans, which has been published in the famous British journal Nature. Based on the high-quality genomic data of mammals such as platypus and echidna obtained by the research team, the results compared the genomic data of humans, marsupials, birds and reptiles, and finally traced back to the source, and obtained the genomic evolutionary information of early mammalian ancestors about 180 million years ago.
(Pictured by Zhou Yang et al.)
"The mammalian ancestral sequences we constructed this time provide important reference information for understanding how mammals, including humans, undergo radiologous adaptive evolution." The first author of the paper, Dr. Yang Zhou, a joint study by the University of Copenhagen in Denmark and the Huada Institute of Life Sciences in Shenzhen, said, "Modern humans have 46 chromosomes, and our common ancestor with platypus is likely to have 60 chromosomes, which have undergone many mutations to form today's state." ”
"Single-porous mammals such as platypus and echidnas are very old taxa, and they are evolutionarily sister groups with all other living mammals and diverged from other mammals about 180 million years ago. Their genomic data can help us understand the common ancestor of mammals 180 million years ago and what has changed in the evolution of different mammal groups over the course of 180 million years. One of the paper's corresponding authors, Professor Frank Gruzner of Australia, said.
It is understood that the study also revealed surprisingly complex patterns in the evolution of mammalian sex chromosomes. "We all know that humans and the vast majority of other mammals determine sex by two chromosomes, X and Y. The XY chromosome determines the male, and XX corresponds to the female. Zhou Qi, another corresponding author of the paper, a professor at the Institute of Life Sciences of Zhejiang University, said, "But our study shows that the sex chromosomes of single-porosity do not have any homologous relationship with the sex chromosomes of most mammals, including humans, but are closer to birds." That is, we and platypus evolved separately and independently of different sex chromosomal systems for about tens of millions of years after our ancestral divergence. ”
"In fact, platypuses have 5 pairs of sex chromosomes, or 10. And we only have 1 pair, that is, 2. "Our research shows that the sex chromosomes of single-porosity have most likely undergone very complex evolution." ”
In addition, the study also revealed a series of special events that occurred during the evolution of platypus and echidnas, such as the loss of some genes related to teeth from the molecular mechanism to find the cause of the complete loss of teeth in these two animals after adulthood, while other preserved genes related to egg formation suggested that single-porosity was a cue of a small number of oviparous mammals.
The study also found that genes encoding the main protein components of mammalian milk already exist in the order Monoammen, indicating that the traits of lactation and milk have evolved in the recent common ancestor of all living mammals.
"Through the latest sequencing technology combined with molecular marker maps, we can obtain higher quality chromosome-level genomic data, and through the algorithms we have established, we can systematically carry out comparative analysis to help us better understand the molecular mechanisms in the evolution of species." The study's corresponding author, Professor Zhang Guojie of the Shenzhen Huada Institute of Life Sciences, the Kunming Institute of Zoology of the Chinese Academy of Sciences, and the University of Copenhagen in Denmark, said: "This study not only reveals how fine chromosomal structural variation processes affect the early evolution of mammals, but also answers the mechanisms by which many special biological traits of many special mammalian taxa of single-porous species are produced." ”
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