Polycistronic
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Messenger RNA (mRNA) is said to be polycistronic when it contains the genetic information to translate more than one protein. Most of the mRNA found in prokaryotes is polycistronic. On the other hand, eukaryotic polycistronic mRNA is very rare. This is because in eukaryotic translation, ribosomes bind to the 7-methylguanosine 'cap' on the 5' end of the mRNA transcript and scan down until the first AUG is reached.
An example of polycistronic mRNA is in the biosynthetic pathway for tryptophan in E.Coli: a single mRNA molecule about 7000 nucleotides long specifies five enzymes, each of which has its own start and stop signals on the mRNA. Another classic example is the lac operon which consists of several genes itself and results in polycistronic mRNA.
Messenger RNA (mRNA) is said to be polycistronic when it contains the genetic information to translate more than one protein. Most of the mRNA found in prokaryotes is polycistronic. On the other hand, eukaryotic polycistronic mRNA is very rare. This is because in eukaryotic translation, ribosomes bind to the 7-methylguanosine 'cap' on the 5' end of the mRNA transcript and scan down until the first AUG is reached.
An example of polycistronic mRNA is in the biosynthetic pathway for tryptophan in E.Coli: a single mRNA molecule about 7000 nucleotides long specifies five enzymes, each of which has its own start and stop signals on the mRNA. Another classic example is the lac operon, which consists of several genes itself and results in polycistronic mRNA after transcription.