FIGURE 96. A section of mRNA passing through a ribosome. Floating nearby are tRNA
molecules, carrying amino acids which are stripped off by the ribosome and appended to the
growing protein. The Genetic Code is contained in the tRNA molecules, collectively. Note how
the base-pairing (A-U, C-G) is represented by interlocking letter-forms in the diagram.
[Drawing by Scott E. Kim.]codon of mRNA clicks into position in the ribosome's "playing head", the
ribosome reaches out into the cytoplasm and latches onto a clover whose
anticodon is complementary to the mRNA codon. Then it pulls the clover
into such a position that it can rip off the clover's amino acid, and stick it
covalently onto the growing protein. (Incidentally, the bond between an
amino acid and its neighbor in a protein is a very strong covalent bond,
called a "peptide bond". For this reason, proteins are sometimes called
"polypeptides".) Of course it is no accident that the "clovers" carry the
proper amino acids, for they have all been manufactured according to
precise instructions emanating from the "throne room".Self-Ref and Self-Rep 523