amino acid's presence means that such-and-such an operation will get
performed". In other words, in real genetics, an individual amino acid's
contribution to the enzyme's overall function is not "context-free". How-
ever, this fact should not be construed in any way as ammunition for an
antireductionist argument to the effect that "the whole [enzyme] cannot be
explained as the sum of its parts". That would be wholly unjustified. What
is justified is rejection of the simpler claim that "each amino acid contrib-
utes to the sum in a manner which is independent of the other amino acids
present". In other words, the function of a protein cannot be considered to
be built up from context-free functions of its parts; rather, one must
consider how the parts interact. It is still possible in principle to write a
computer program which takes as input the primary structure of a protein,
FIGURE 95. The structure of myoglobin, deduced from high-resolution X-ray data. The
large-scale "twisted pipe" appearance is the tertiary structure; the finer helix inside-the
"alpha helix"~s the secondary structure. [From A. Lehninger, Biochemistry.]Self-Ref and Self-Rep^521