In which of the following phenomena does failure of cytokinesis after telophase stage of cell division result in an increase in a whole set of chromosomes in an organism?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Polyploidy
Chromosomal disorders arise when chromosomes are absent, in excess or wrongly arranged. If the cell copies its chromosomes but cytokinesis fails after telophase, the cell keeps an extra whole set of chromosomes. This is polyploidy, and it is often seen in plants.
Option (1) Aneuploidy — Incorrect. Aneuploidy is the gain or loss of one or a few chromosomes. It is caused by failure of segregation of chromatids during cell division, not by failure of cytokinesis, and a whole set is not added.
Option (2) Polyploidy — Correct. Polyploidy is the increase in a whole set of chromosomes that results when cytokinesis fails after telophase.
Option (3) Inversion — Incorrect. Inversion is a change in the arrangement of genes within a chromosome, where a segment is turned around. The number of chromosomes does not change.
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.”