| aneuploidy | One or a few chromosomes above or below the normal chromosome number. For example, three number 21 chromosomes or trisomy 21 (characteristic of Down syndrome) is a form of aneuploidy. (12 Dec 1998) |
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| partial aneuploidy | A type of mosaicism in which some cells have a normal number of chromosomes and some have an abnormal number. (05 Mar 2000) |
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