- The COL6A1 and COL6A2 genes exist as a gene cluster and detect highly informative DNA polymorphisms in the telomeric region of human chromosome 21q. Francomano, C.A., Cutting, G.R., McCormick, M.K., Chu, M.L., Timpl, R., Hong, H.K., Antonarakis, S.E. Hum. Genet. (1991)