Genomes are often described as recipe books for living things.
If that’s the case, many of them badly need an editor. For
example, around half of the human genome is made up of bits of
DNA that have copied themselves and jumped around, creating vast
tracts of repetitive sequences. The same is true for the cow
genome, where one particular piece of DNA, known as BovB, has
run amok. It’s there in its thousands. Around a quarter of a
cow’s DNA is made of BovB sequences or their descendants. BovB
isn’t restricted to cows. If you look for it in other animals,
as Ali Morton Walsh from the University of Adelaide did, you’ll
find it in elephants, horses, and platypuses. It lurks among the
DNA of skinks and geckos, pythons and seasnakes. It’s there in
purple sea urchin, the silkworm and the zebrafish. The obvious
interpretation is that BovB was present in the ancestor of all
of these animals, and stayed in their genomes as they
diversified. If that’s the case, then closely related species
should have more similar versi