Nondisjunction affects chromosomes how?

Nondisjunction is the process where chromosomes fail to separate properly during cell division, specifically during meiosis or mitosis. When this error occurs, it leads to gametes (sperm or eggs) that have an abnormal number of chromosomes. When such gametes fuse during fertilization, the resulting zygote also ends up with an abnormal chromosome number. This condition is known as aneuploidy, which can result in various genetic disorders, such as Down syndrome, Turner syndrome, or Klinefelter syndrome.

The other options do not accurately reflect the effects of nondisjunction. For instance, while mutations in DNA can occur due to various factors, nondisjunction specifically refers to chromosome separation errors, not direct mutations in the DNA sequence. The statement about replicating chromosomes incorrectly may relate to other cellular processes, but nondisjunction itself is more about the failure of chromosomes to segregate rather than an error in replication. Moreover, nondisjunction does not increase genetic diversity; rather, it often leads to disorders due to an abnormal chromosomal makeup. The key aspect of nondisjunction is its direct result of creating cells with an abnormal number of chromosomes, leading to significant developmental and health issues.