Genome and evolvability: study layers that modify (Introduction)

by David Turell , Wednesday, April 03, 2024, 19:43 (30 days ago) @ David Turell

Role of the centrosome is studied:

https://phys.org/news/2024-04-view-centromere-variation-evolution.html

"A genomic study of human and selected nonhuman primate centromeres has revealed their unimaginable diversity and speed of evolutionary change.

"In cell genetics, a centromere is the spot where two sister chromatids attach. A chromatid is one-half of a duplicated chromosome. United pairs of chromosomes have identifiable shapes because centromeres are not in a uniform position. As a cell prepares to divide, the machinery to separate and segregate chromosomes goes into action at each centromere location.

"Unless the genetic material is distributed correctly between the two resulting cells, problems can arise. These include cancer, congenital disorders such as Down syndrome, and the inability of a fertilized cell to grow into a baby.

"Although centromeres are vital to proper cell replication, the complexity of their genomic organization had been almost impossible to study. The lack of centromere sequences hindered exploration of how these regions help maintain genetic integrity.

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"A first look at the factors behind the vast variations in centromeres is reported on April 3, in Nature. The findings suggest that centromeres are likely highly individualized among people. A set of centromeres might even be a personal signature, just as we each have characteristic voice patterns, iris colorations and fingerprints that distinguish us from one another.

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"Only the human X chromosome appears to be mostly immutable, with very similar sequences and structure across a diversity of humans.

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"To capture information on how human centromeres might have evolved, the team compared human genetic sequences of two completely sequenced human centromeres with those of some nonhuman primates. These were the chimpanzee and the orangutan, which are great apes and closely related species to humans, and the macaque, an Old-World monkey and a more distant relative.

"The scientists discovered that centromeres have been evolving much faster than other unique portions of the human genome. They are among the most mutation-prone regions of the human genome. The researchers also found that the unique sequences and structure of centromeres were the culmination of different evolutionary forces moving at different rates. (my bold)

"'The rapid mutation of the centromeric regions of the genome, along with their various mutation rates, has led to their diverse structure and organization," Logsdon noted. It was surprising to learn, the scientists said, that such vital areas of the genome were subject to swift changes, because, in general, critical functions tend to be genetically conserved."

Comment: this supports other work, reported here, of HAR (human active regions) areas of human chromosomes. Our genome is specifically different because we are so unusual. All in support of Adler, who argued from a Darwin theory standpoint, we are an unexpected extraordinary endpoint.