They replace adenine with “so-called diaminopurine”:
“It’s been known that there’s this phage that doesn’t have adenine in its genome . . . and it’s been an unsolved mystery about how it does that,” says Jef Boeke, a molecular biologist at New York University Grossman School of Medicine who was not involved in the work. These papers “spell that out in glorious molecular detail,” he tells The Scientist. Plus, the authors “have done an amazingly comprehensive job of showing that this is not one crazy outlier, but there’s a whole group of bacteriophages that have this kind of genetic material.” …
“There are a lot of questions that remain unanswered,” says Kaminski. In a paper that came out earlier this month on which he’s a coauthor, researchers shed light on one of those questions—how the S-2L genome is copied—by identifying the relevant polymerase. But Kaminski explains that one of the most difficult questions to answer will be when this mechanism evolved. “It’s supposed to be ancient because it roots deeply in the phylogenetic tree and because of the similarity of the [enzymatic] structures,” but it’s not clear whether Z or A genomes came first.Abby Olena, “Some Viruses Use an Alternative Genetic Alphabet” at The Scientist
This is a problem, all right. But really, why do these, or any life/quasi-life forms, have a “genetic alphabet” (an alphabet of life, not learning) at all if everything happened by natural selection acting on random mutation, as the textbooks claim? Let alone an alphabet of life they can just substitute some other letters for? Is there anyone out there who can do the math?
This is like discovering that your new Newfoundland Rescue Dog speaks English with an Eastern Canadian accent.
Of course, if you are a good Darwinist, it’s the accent you focus on, right, not what the dog just said…
See also: Interesting finding: COVID-19 populations show high convergent evolution. Researchers: We find that two particular mutation rates, G →U and C →U, are similarly elevated and considerably higher than all other mutation rates, causing the majority of mutations in the SARS-CoV-2 genome, and are possibly the result of APOBEC and ROS activity.