The cell's DNA is replicated in S phase and segregated in M phase (mitosis). In somatic cells, these phases are separated by gaps: G1 (unreplicated chromosomes) and G2 (replicated chromosomes).

This extra support allows high-affinity B cells to move quickly through the cell cycle and spend less time in the G0/G1 phase where hypermutation occurs. Meanwhile, B cells that have yet to win the ...