Transciprition in prokaryote vs eukaryote

[m25]

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So during DNA replication, prokaryotes have only one origin of replication/replication fork while eukaryote have multiple origin of replication/replication fork. What about their differences during transcription? Are genes only transcribed at a time in eukaryotes vs. multiple genes transcribed at a time in prokaryotes, or are multiple genes transcribed at a time in both eukaryotes and prokaryotes?

 

[krukshanks]

What do you mean by "at a time"? If you are referring to polycistronic, then polycistronic transcripts (a single mRNA encoding multiple proteins) are only formed in prokaryotes.

 

[azor ahai]

Transcription is just like replication except it forms an mRNA - this is pre-mRNA for eukaryotes because it still must undergo splicing and capping before it leaves the cytoplasm. This is not necessary for prokaryotes. In fact, transcription and translation often occurs simultaneously in prokaryotes because there is no compartmentalization. As to whether genes are transcribed one at a time or several at a time is irrelevant. What is transcribed is dependent upon promoter sequences and termination sequences. However, it is true that the eukaryotic mRNA will code for one protein (composed of multiple AA's which the individual codons code for) while the prokaryotic mRNA can code for more than one protein which makes it polycistronic. An example of the latter is the lac operon in e. coli.