FIGURE 1.

Diagram of the murine IgH locus. Not drawn to scale. Coding sequences (e.g., V, D, J, and C gene segments) are shown as rectangles. C region segments are identified by Greek letters (µ, δ, etc.). Regulatory sequences are shown as horizontal ovals (e.g., Eµ) and the IgH 3′RR shown covers the DNase I HS sites hs3a, hs1,2, hs3b, and hs4. Vertical ovals upstream of each C region gene signify the “switch regions” in which breaks occur during CSR.