Without centromeres, cells cannot divide properly ... With a few exceptions, eukaryotic chromosomes have a single centromere that ensures their accurate segregation during mitosis.

How B cells somehow rapidly mutate and improve all at once was a long-standing mystery. Now, advanced imaging techniques ...

so that diploid daughter cells are produced. (B) In meiosis, two chromosome-segregation phases, meiosis I and meiosis II, follow a single round of DNA replication during the premeiotic S phase.