The gain or loss of one or more chromosomes from a normal set, as seen in Trisomy and Monosomy, is called what?

1. A change in chromosome number can be a whole-set change or a single-chromosome change. 2. The loss or gain of one or more individual chromosomes is called aneuploidy. 3. Trisomy (2n+1) and Monosomy (2n-1) are examples of aneuploidy. 4. Euploidy involves whole extra sets such as 3n or 4n, which rules out option A. 5. So the condition is aneuploidy, option B. _Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 18 Genetics "Mutation", p.277_