74 



Martynas Ycas 



collected in Table I. Mutations (as inferred from differences between homo- 

 logous proteins) do not produce a general scrambling of protein sequence, 

 but a replacement of one or more residues, leaving the rest of the sequence 

 unchanged. Since homologous proteins can differ by a one residue replacement, 

 it is clear that individual residues, rather than groups of residues, are represented 

 in the genetic material. 



Table I. Sequences in Homologous Proteins from Different Species 

 Protein Species 



Insulin (34) 



. cys-thr-ser-ileu-cys . 

 . cys-ala-ser-val-cys . . 

 . cys-ala-gly-val-cys . . 

 . cys-thr-gly-ileu-cys . 

 . cys-thr-ser-ileu-cys . 



Pig 



Cattle 

 Sheep 

 Horse 

 Whale 



