Amazing stuff!
"Some 180 million years ago, there lived an early mammal ... that became the earliest-known ancestor to all mammals on Earth ...
an international team of researchers has now computationally reconstructed the organization of its genome. ...
the team analyzed high-quality genome sequences from 32 living mammal species, including humans, manatees, bats, pangolins, rabbits and wombats, using the genomes of chickens and Chinese alligators as comparison groups from outside the mammalian class. ...
The team found 1,215 blocks of genes that consistently appear, in order and on the same chromosome, across all 32 genomes. The researchers deduced that our common ancestor had 21 chromosomes, including 19 autosomal chromosomes and two sex chromosomes. They found nine whole chromosomes, or fragments thereof, where the order of genes matched up perfectly with the chromosomes of modern birds, demonstrating the extraordinary stability of some genetic sequences, even across more than 300 million years of evolution. ..."
an international team of researchers has now computationally reconstructed the organization of its genome. ...
the team analyzed high-quality genome sequences from 32 living mammal species, including humans, manatees, bats, pangolins, rabbits and wombats, using the genomes of chickens and Chinese alligators as comparison groups from outside the mammalian class. ...
The team found 1,215 blocks of genes that consistently appear, in order and on the same chromosome, across all 32 genomes. The researchers deduced that our common ancestor had 21 chromosomes, including 19 autosomal chromosomes and two sex chromosomes. They found nine whole chromosomes, or fragments thereof, where the order of genes matched up perfectly with the chromosomes of modern birds, demonstrating the extraordinary stability of some genetic sequences, even across more than 300 million years of evolution. ..."
"... “This remarkable finding shows the evolutionary stability of the order and orientation of genes on chromosomes over an extended evolutionary timeframe of more than 320 million years,” ...
“Ancestral genome reconstructions are critical to interpreting where and why selective pressures vary across genomes. This study establishes a clear relationship between chromatin architecture, gene regulation and linkage conservation,” ... “This provides the foundation for assessing the role of natural selection in chromosome evolution across the mammalian tree of life.” ..."
“Ancestral genome reconstructions are critical to interpreting where and why selective pressures vary across genomes. This study establishes a clear relationship between chromatin architecture, gene regulation and linkage conservation,” ... “This provides the foundation for assessing the role of natural selection in chromosome evolution across the mammalian tree of life.” ..."
From the abstract:
"Decrypting the rearrangements that drive mammalian chromosome evolution is critical to understanding the molecular bases of speciation, adaptation, and disease susceptibility. Using 8 scaffolded and 26 chromosome-scale genome assemblies representing 23/26 mammal orders, we computationally reconstructed ancestral karyotypes and syntenic relationships at 16 nodes along the mammalian phylogeny. Three different reference genomes (human, sloth, and cattle) representing phylogenetically distinct mammalian superorders were used to assess reference bias in the reconstructed ancestral karyotypes and to expand the number of clades with reconstructed genomes. The mammalian ancestor likely had 19 pairs of autosomes, with nine of the smallest chromosomes shared with the common ancestor of all amniotes (three still conserved in extant mammals), demonstrating a striking conservation of synteny for ∼320 My of vertebrate evolution. The numbers and types of chromosome rearrangements were classified for transitions between the ancestral mammalian karyotype, descendent ancestors, and extant species. For example, 94 inversions, 16 fissions, and 14 fusions that occurred over 53 My differentiated the therian from the descendent eutherian ancestor. The highest breakpoint rate was observed between the mammalian and therian ancestors (3.9 breakpoints/My). Reconstructed mammalian ancestor chromosomes were found to have distinct evolutionary histories reflected in their rates and types of rearrangements. ..."
Phylogenetic tree of descendant species and reconstructed ancestors.
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