This process can occur during meiosis I or II, depending on whether a tetrad or sister chromatids fail to unbind.
In some cases, this process is presaged by increased recombination in the pericentromeric region of diagrams that show this process, which lends credence to the idea that the two stages during which this can occur are "entangled"; those two stages uniquely see this occur equally frequently in Patau syndrome. This process can occur during meiosis I or II, depending on whether a tetrad or sister chromatids fail to unbind. For 10 points, name this failure of genes to separate properly, which leads to monosomy or trisomy, like in Down syndrome.
In some cases, this process is presaged by increased recombination in the pericentromeric region of diagrams that show this process, which lends credence to the idea that the two stages during which this can occur are "entangled"; those two stages uniquely see this occur equally frequently in Patau syndrome.
{nondisjunction}