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Genetic Linkage

On COVID Origin and Omicron Persistence: This Geneticist’s View

The latest phrase borrowed from biology in COVID conversations is convergent evolution. It refers to pairs of unrelated species that look similar because their ancestors evolved under similar environmental conditions. Natural selection favored adaptive (helpful) inherited traits, and millennia later, two unrelated species of mammals or birds look remarkably alike.


Convergent evolution happens to viruses, too. It is unspooling right now as SARS-CoV-2 genome evolution coalesces into variations on the Omicron theme.


The natural history of SARS-CoV-2 began with the wild type, another term from classical genetics. It means "most common," not "normal" as the media often misuses it.


As the virus changed, we grouped sets of new mutations, which substitute one RNA base of the genome at a time, into "variants." We named them, which biologists tend to do.


Alpha, recognized in November 2020, begat beta, gamma, and delta, all of which stayed with us for a bit. The next few versions were fleeting. The International Committee on Taxonomy of Viruses and WHO skipped Nu (because it sounds like "new") and Xi (a common surname), landing on Omicron. And natural selection has favored its collection of mutations. No new Greek letters necessary.


When Species Look Alike


Biologists term traits that are alike in two species that arise from recent shared ancestors homologous, while similar structures or behaviors that arise from similar environmental exposures are analogous. Convergent evolution reflects responses to similar environments (analogy), rather than descent from recent shared ancestors (homology).


Striking examples of convergent evolution are pairs of placental mammals and Australian marsupials. These include anteaters, moles, wolves, ocelots and native cats, flying squirrels and flying phalangers, and groundhogs and wombats.


To continue reading, go to DNA Science, where this post first appeared.

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