“Micro homology”. Wut?

I ranted in a previous post about the use of homology as a quantitative term, rather than a qualitative term. Ben Blackburne commented on that post introducing me to “micro homology”, a term I did not know existed. I ignored its existence, until I heard it spoken yesterday at a talk, which sort of rubbed me the wrong way. Going back to my office to chill, I discovered there are 152 papers indexed in PubMed that use that term in their abstract or title. Not a good way to chill… here we go again: misusing “homology” by overselling it. Apparently microhomology is used to indicate an identity of a short nucleotide sequences in two non-complementary DNA strands. This identity may facilitate strand annealing constructions of chromosomal breakpoints such as the proposed Microhomology-Mediated Break-Induced Replication or microhomology-mediated end joining for DNA repair. There should  be a term for this phenomenon, but why use “microhomology“? The use of “homology” implies that the short identical sequences originated from a common ancestor. “Micro” would mean short region from otherwise homologous sequences. This is possibly derived from “homologous recombination“, where, indeed, homologous sequences are involved.  But in the microhomology case, it may not be so. Also, even if the identity is between short subsequences of otherwise homologous sequences, “microhomology” is somewhat of a confusing term, as it implies a quantitative relationship.  Why not simply use “microidentity” as a drop-in replacement? (Heh: non-homologous replacement).

Of course nothing will change, since I am too late in the game, no one listens to me anyway and I do not see the six readers of this blog rallying to eradicate microhomology.

No I am not bitter. Mild and bitter perhaps, but only after 5 o’clock.


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3 Responses to ““Micro homology”. Wut?”

  1. John says:

    Without proper context I would interpret ‘microhomology’ as ‘extremely low similarity between homologous sequences’ and that would be a guess, because as you say, it does not make much sense. So besides the use of homology in the word, it’s just a weird looking and badly chosen word.
    Anyway, you have 164 subscriptions to your RSS feed in Google Reader, so I guess there should be more than 6 people reading your blog, though you might not notice in terms of actual traffic to your site 🙂


  2. Arjun says:

    Microhomology would be annoying to me too. I haven’t heard it used yet, but I would assume it means a very small true homology surrounded by not homologous stuff of some kind. Not something that has similar sequence. Since the sequences would not necessarily be completely identical I vote for ‘Microsimilarity’.

  3. Marc RR says:

    That one’s new to me. We collected a few here, if you want to have fun browsing: