  In the process of translation, ribosomes read the genetic code on an mRNA and
assemble the corresponding polypeptide chain. The ribosomes perform discrete
directed motion which is well modeled by a totally asymmetric simple exclusion
process (TASEP) with open boundaries. Using Monte Carlo simulations and a
simple mean-field theory, we discuss the effect of one or two ``bottlenecks''
(i.e., slow codons) on the production rate of the final protein. Confirming and
extending previous work by Chou and Lakatos, we find that the location and
spacing of the slow codons can affect the production rate quite dramatically.
In particular, we observe a novel ``edge'' effect, i.e., an interaction of a
single slow codon with the system boundary. We focus in detail on ribosome
density profiles and provide a simple explanation for the length scale which
controls the range of these interactions.
