The tantalizing final sentence to James Watson and Francis Crick's landmark 1953 paper in Nature introducing the genetic material, DNA, is almost as famous as the report itself:
"It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material."
That copying mechanism gone awry spawns the mutations that create new viral variants.
Mutation, Natural Selection, and Recombination, Oh My!
Like Dorothy of Wizard of Oz fame exclaiming "lions and tigers and bears, oh my!" three major forces of nature set the stage for genome evolution: mutation, natural selection, and recombination.
The virus we're battling has a single strand of RNA for its genetic material, and not the more familiar double-stranded DNA. But an RNA genome must also replicate – copy itself – when one virus becomes two. And mistakes, mutations, can happen when they do so, like perpetuating a typo when copying a document.
"Every chance a virus has to replicate it can come up with a new strategy to evade the immune system," said Bruce Walker, MD, Director of the Ragon Institute of MGH, MIT and Harvard, at a recent press briefing of the Massachusetts Consortium on Pathogen Readiness (MassCPR). That's too teleological an explanation for me – a virus doesn't intentionally change itself into a fitter form. Instead, mutations tend to arise at genome locations where the sequence is repetitive, like CGCGCGCG compared to ACGCCUCGAU. It's easier to mistype when "the" is next to "they" in a document, compared to "hippopotamus" next to "diarrhea."
To continue reading, go to DNA Science, where this post first appeared.
