Strange genes

There are a surprising number of species of birds, and of song birds in particular. Recent evidence that all songbirds share a chromosome that is propagated only through germ cells, not present in somatic cells, might help explain that. (Cite.)

The biology taught when I was young focused on nuclear DNA as the mechanism of evolution. That was the modern synthesis, with Fisher and Haldane providing its mathematical basis. Mitochondrial DNA was just carried along. Well, the rule is that biology is always weirder than current theory teaches. Mitochondrial mutations may create conflicts with nuclear DNA that help drive speciation.

Scientists at Emory and Princeton have explored the space of other molecules that could act like nucleic acids, in forming sequences that encode proteins. They found millions. Biology is ridiculously path dependent, both at the level of individual development, and at the level of overall evolution. The reason all life shares one genetic code is because it all descended from the earliest progenitors that had that genetic code. How that came about is one of the great mysteries. (Cite.)

Gryphons are impossible, despite their popularity in art, for reasons every beginning biology student should be able to explain.