To take the quiz — or to play along — here’s your background information, and no cheating by looking into cell biology textbooks or using Google or PubMed.
1. Topoisomerases are essential enzymes, found in all organisms, which solve topological problems arising from the double-helical structure of DNA.
2. All organisms on Earth share a common ancestor, the Last Universal Common Ancestor (LUCA).
OK — quiz time. Given (1) and (2), what should we expect to find, with respect to the homology of topoisomerases, when we examine organisms descended from LUCA in different parts of the Tree of Life?
A) Homologous topoisomerases
B) Non-homologous topoisomerases
C) Can’t say.
Make your best guess, and then go here:
[This paper is open access.]
Don’t miss the authors’ comment 12 lines down, in the right-hand column, first page.
Agree or disagree?