Simple question: aneusomy vs aneuploidy - what's the difference?

I tried google and PubMed, but although there are articles talking about aneusomy, I wasn't able to find a clear definition contrasting the two.

I have no formal genetics training, so sorry if this seems trivial!

  • $\begingroup$ Can you quote definitions for each term from the citations you've found to clarify what you don't understand about the difference between the terms? $\endgroup$ Jun 16, 2021 at 20:27

1 Answer 1


The suffixes -somy and -ploidy mean different things. The suffix -somy translates to "body" and in genetics typically refers to an individual chromosome. Ploidy level, on the other hand, refers to the full chromosome complement.

For example, most human cells are diploid - they have two copies of every chromosome. The number of chromosomes in a diploid cell is 46. Now, if there was an extra of one of those chromosomes, we would have a trisomy of that chromosome (e.g., Trisomy 21 refers to having an extra chromosome 21, but still has only 2 of every other chromosome). If there was one extra of every chromosome, that would be called triploidy (this actually does happen in plants).

Aneuploid comes from the word euploid - which refers to the "true" amount of chromosomes that should be in a cell. If something is aneuploid (i.e., not-true), there is something wrong with the amount of chromosomes. Aneusomy would refer to the chromosomes, while aneuploidy refers to the chromosome set.

This article from NCBI gives a good overview of aneuploidy, but also monosomy, trisomy, etc.

This page from Khan Academy may be a little more non-biologist friendly.

In my experience I have encountered "aneuploidy" much more than "aneusomy" as a descriptor. It may be that in certain fields of genetics one is more relevant or common than another.


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