HB F-Yamaguchi (gamma 75Thr, gamma 80Asn, gamma 136Ala) is associated with G gamma-thalassemia.

Restriction endonuclease and analyses of DNA from a known Hb F-Yamaguchi heterozygote and three of his relatives have shown a deletion of about 5 kb, which includes one of the gamma genes. This abnormality is similar to the G gamma-thalassemia described recently [4] and is probably caused by an unequal crossing over between-G gamma- and -A gamma T-genes. The abnormal-G gamma A gamma T-X-(X = Asp leads to Asn at gamma 80) hybrid gene produces the gamma-Yamaguchi chain at a level usually seen for G gamma chains only.