What mutation involves chromosomes separating incorrectly during cell division, possibly leading to an extra chromosome?

Nondisjunction is a type of mutation that occurs when chromosomes fail to separate properly during cell division, specifically during meiosis or mitosis. This failure can lead to an abnormal number of chromosomes in the resulting daughter cells. When nondisjunction takes place during the formation of gametes (sperm or egg), it can result in zygotes with an extra chromosome, a condition known as aneuploidy.

For example, if nondisjunction occurs and an egg retains an extra copy of chromosome 21, it may lead to Down syndrome in the resulting offspring, who would then have three copies of that chromosome instead of the usual two. This illustrates how nondisjunction can directly result in significant genetic conditions due to the presence of an extra chromosome.

In contrast, inversion mutations involve segments of DNA breaking off and reattaching in reverse order, which does not lead to an extra chromosome. Translocation mutations involve a segment of one chromosome breaking off and attaching to another chromosome, again not resulting in additional chromosomes. Duplications involve the repetition of a section of the chromosome, which can lead to additional genetic material, but not through improper separation during cell division. Therefore, the definition and consequences of nondisjunction align perfectly with the