This month in The Journal

Nondisjunction, the failure of chromosomes to separate, results in aneuploidies, in which cells have an abnormal number of chromosomes. Centromeres play an essential role in segregation of homologous chromosomes and sister chromatids. It has been hypothesized that centromere size, sequence, allelic difference, and epigenetic features might influence nondisjunction and, therefore, aneuploidy risk. Until recently, however, it has been difficult to study the sequence of human centromeres due to limitations of short-read sequencing.