Silent Code (IMAGE) University of Pennsylvania Caption β-actin and γ-actin are nearly identical proteins, differing by only four amino acids (in red). But they contain many more differences in their nucleotide sequence, and this "silent code" is responsible distinct functions of the two proteins, the researchers found. Credit University of Pennsylvania Usage Restrictions In context of reporting License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.