Fig. 1.

Selection on speed and accuracy. (A) Free ribosomes initiate translation of an mRNA and begin elongation. Initiation is rate limiting for translation, and the availability of free ribosomes is affected by the rate of elongation, as the quicker a ribosome completes elongation and termination, the sooner it may initiate on another mRNA. Some proteins are produced with errors or mistranslation events. Though errors are rare, mistranslated proteins are more likely to misfold. (B) The number of ribosomes occupied, and the number of misfolded proteins produced, per gene, are each proportional to gene expression.