These types of problems can sometimes be avoided by using cell-free extracts for the in vitro expression of proteins. In vitro translation systems are also useful for other applications, including incorporating modified or unnatural amino acids for functional studies and localizing mutations via synthesis of truncated gene products. The RNA can be total RNA, mRNA, or a synthesized template. RNA is transcribed from the DNA template, then subsequently translated without purification. In vitro translation In coupled systems, transcription and translation occur in the same tube.
Kits utilizing both prokaryotic and eukaryotic lysate systems are commercially available.
Transcription and translation occur simultaneously within prokaryotic cells. During transcription, the 5' end of RNA is available for ribosomal binding. Translation commences while the 3' end is still being transcribed. In eukaryotes, by contrast, transcription and translation occur in separate compartments at different times. Conditions that allow both transcription and eukaryotic translation to occur in a single tube may be suboptimal for one or both reactions.