unusual combinations -- unexpected sets , excess of lack -- of antigenic determinants , or gm allotypes , on the constant regions of the heavy chains of the human igg1 and igg3 immunoglobulins are accounted for in terms of genetic events ( exchanges , duplications and deletions ) involving the dna sequences , or exons , coding for the three ch1- , ch2- and ch3 domains of the gamma 1 and gamma 3 chains .
C1420192
heavy chains
C0086418
human