During B cell maturation,immunoglobulin genes undergo rearrangement. 2.YH-->D Rearrangement VH Cu Cs Cy3 Cy1 Cy2b Cy2a Ca Co 5☒2☒工H州圆■■圆圈圈圈■3 ④ The section between the apposed D region and a V region loops out 5'3H2—■ 5'3☒2☒■■ ⑤ Excision of the loop ⑥ Result:Apposition of the V and D and J regionsDuring B cell maturation, immunoglobulin genes undergo rearrangement