Interlocus gene conversion from FCGR3B to FCGR3A. The FCGR3A gene encodes a receptor for the Fc portion of immunoglobulin G, which is involved in the removal of antigen–antibody complexes from the circulation. The highly similar paralog, FCGR3B, which resides only 73 kb downstream from FCGR3A, encodes a shorter protein due to differences in the positions of both the start and stop codons. Coding exons are shown as filled boxes, UTRs as empty boxes. Introns are represented as lines and are not drawn to scale. The black asterisks indicate the normal stop codons of the FCGR3A and FCGR3B genes; the gray asterisk identifies the premature stop codon in the FCGR3A gene that is introduced by an IGC event with FCGR3B.