During what process are chromosomes expected to separate correctly to avoid non-disjunction?

The process during which chromosomes are expected to separate correctly to avoid non-disjunction is meiosis. This is a specialized type of cell division that reduces the chromosome number by half, producing four haploid cells from one diploid cell.

During meiosis, specifically in anaphase I and anaphase II, homologous chromosomes and sister chromatids are separated, respectively. Proper segregation of these chromosomes is crucial because if a mistake occurs during this process and the chromosomes do not separate correctly, non-disjunction can happen. Non-disjunction leads to gametes with an abnormal number of chromosomes, which can result in conditions such as Down syndrome when these gametes participate in fertilization.

In contrast, mitosis is a form of cell division that results in two identical daughter cells and is usually not associated with the unique chromosome segregation challenges present in meiosis. Fertilization involves the fusion of gametes, while cell differentiation refers to the process by which cells become specialized and does not directly pertain to chromosome segregation. Thus, meiosis is the critical process for preventing non-disjunction through proper chromosome separation.