The sentence I'm thinking about is:

Trisomy is an aneuploidy (numerical chromosomal mutation) in which a chromosome is over-represented once.


Organisms like human beings have a pair of each type of chromosome; two Chr-1 two Chr-2 ..... two Chr-23; it has a pair of 23 chromosomes. So they are called diploids(2n, n=total types of chromosome, 23 in humans) (di means two). Now, Trisomy is a condition in which a diploid organism happens to have an extra copy of a particular chromosome (2n + 1), i.e. they have three copies of that chromosome and I'm trying to bring out the presence of a single extra copy of chromosome in the definition.


I want to use a similar phrase to define tetrasomy too in which there are four copies of a particular chromosome- ....over-represented twice.

Can once be used with over-represented/under-represented in this way? If not how can it be framed?

  • It is not gibberish. It is a background of the scientific term Trisomy.
    – Tyto alba
    Commented Feb 20, 2017 at 7:25
  • We often find the verb represented in scientific writing about chromosomes. But over-represented once is a rather clunky phrase. What is wrong with "there is one additional pair" and " there are two additional pairs" etc etc?
    – TimR
    Commented Feb 20, 2017 at 12:19

1 Answer 1


While certainly not a common construct, over-represented once seems to make sense and be grammatical in your example. What sounds awkward to me is that once typically has an association with time, but in the example the association is with quantity. That doesn't make its usage here incorrect, however. It is perfectly fine to say, "It only replicated itself once." There is little difference between that usage and the geeky phrase, "over-represented once".

More common English might word it as, "... in which a chromosome occurs one time too many."

  • one time too many - I don't get this. Besides I've made some edit to fully explain what I intend to sound.
    – Tyto alba
    Commented Feb 20, 2017 at 8:02
  • How about writing Trisomy is an aneuploidy (numerical chromosomal mutation) in which a chromosome is over-represented one time?
    – Tyto alba
    Commented Feb 20, 2017 at 8:04
  • @SanjuktaGhosh "... over-represented one time" is okay, but still feels as awkward as it did ending with once. I don't know cellular biology: is the term over-represented common in that field? Unless there is a reason to use that particular term, my suggestion is to avoid. It is uncommon in English to associate any given number with it. (Not wrong, just uncommon.)
    – RichF
    Commented Feb 20, 2017 at 8:31
  • Not that it is common, found that in a book that is highly recommended for my course, it's genetics. These terms trisomy and tetrasomy are not quite well defined in most of the sources I have found. Well I'll use it until I find something suitable to replace.
    – Tyto alba
    Commented Feb 20, 2017 at 9:04
  • once is associated with count. How many times did you see the movie? Once.
    – TimR
    Commented Feb 20, 2017 at 12:24

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