Failure of chromatids to segregate during cell division cycle results…

The correct answer is Option (3) → Aneuploidy

Option (1) Polyploidy — Incorrect. Polyploidy is the gain of a whole set of chromosomes. It follows a failure of cytokinesis, not a failure of chromatids to separate.

Option (2) Euploidy — Incorrect. In euploidy the chromosome number is a whole multiple of the basic set (n, 2n, 3n and so on). No single chromosome is gained or lost.

Option (3) Aneuploidy — Correct. One or a few chromosomes are gained or lost, so the number is no longer a whole multiple of the set.

Option (4) Autopolyploidy — Incorrect. Autopolyploidy is polyploidy in which the extra sets come from the same species, by the doubling of its own chromosome sets. It also involves whole sets.

Note: A similar question was also asked in CUET (UG) 2026 on 20-05-2026 (Slot 1).

NCERT Extract:
Chromosomal Disorders – “… Failure of segregation of chromatids during cell division cycle results in the gain or loss of a chromosome(s), called aneuploidy. For example, Down’s syndrome results in the gain of extra copy of chromosome 21. Similarly, Turner’s syndrome results due to loss of an X chromosome in human females. Failure of cytokinesis after telophase stage of cell division results in an increase in a whole set of chromosomes in an organism and, this phenomenon is known as polyploidy. This condition is often seen in plants.”