What is the term for the failure of homologous chromosomes or sister chromatids to separate properly during meiosis?

The failure of homologous chromosomes or sister chromatids to separate properly during meiosis is referred to as non-disjunction. This process results in gametes that contain an abnormal number of chromosomes. If non-disjunction occurs during the formation of egg or sperm cells, it can lead to conditions such as Down syndrome, where there is an extra copy of chromosome 21.

During meiosis, chromosomes normally undergo a series of steps to ensure that they are separated and distributed evenly into the resulting gametes. However, if they fail to separate, one gamete may receive two copies of a chromosome, while another may receive none. This improper distribution leads to aneuploidy, which can have significant developmental consequences for an organism.

The other terms in the context of meiosis refer to different processes: crossing over is related to the exchange of genetic material between homologous chromosomes, independent assortment refers to the random distribution of maternal and paternal chromosomes to the gametes, and segregation describes the separation of alleles during gamete formation. None of these terms accurately describes the specific failure of chromosome separation that occurs in non-disjunction.