401056 7 Se ‘put 2199p ASE Transcription and translation of the genetic message in cells are not infinitely precise and OrGec [9] has suggested that errors in protein synthesis may become more numerous with age and that the accumulation of'errorcontaining proteins could contribute to the ageing process. Indeed, Lewis and TaRRANT [5] have presented evidence for the accumulation ofaltered inactive lactic dehydrogenase molecules in cultures of humanfibroblasts prior s iB t S & AYHOLISOd3Su TE \ fir Introduction XN comv7S7 7SUVUP Biology Division, Onk Ridge National Laboratory, Oak Ridge, Tenn., and Brookhaven National Laboratory, Upton, N.Y. S NOWOSTIOD R.A. Popp, E.G. Baicirr, G.P. Hirscu, and R. A. CONRAD Ooo ott) =e oF] Errors in Human Hemoglobin as a Function of Age! 30104 Interdiscip!, Topics Geront., vol. 9, pp. 209-218 (Karger, Basel 1976) frequency of about 3 per 10,000 residues; in the latter study where a better defined protein anc better purification procedures were used, valine was found to substitute for isoleucine at two positions in rabbit hemoglobin ata frequency of 2-6 per 10,000 residues. 1 Research supported by the US Atomic Energy Commission under contract with Union Carbide Corporation and by Ageing Research Training grant (PHS grant HO 00296 from NICHHD). SO12b1S eR ee ' . “ ‘ ot ft oof ea aa ' a ats a: ' . . ./ a . a “yet . t4 a ‘ ‘ . . yyw) yaawesoy [Rupe AL former study, valine or leucine was found to substitute for isoleucine at a Agopusouery TRuOeN woAeyppoolg. [4] have shown that fructose-1,6-diphosphate aldolase in livers of old miceis similarly altered; the specific activity of aldolase in the livers of old mice is only half that in young mice. They suggested that the inactive molecules may contain errors of mistranslation which arose at an increased frequency as the tissue culture cells and mice age. LoFrFieLp [6] and LofrrFiELD and VANDERJAGT [7] have measured the frequency of substitution of one amino acid for another during the synthesis of egg albumin and rabbit hemoglobin. In the 410K MON “TTT ‘UOdg to the death of these established cell lines. Moreover, GERSHON and GERSHON