In this video, we're going to do a brief review of prokaryotic and eukaryotic gene expression by completing all of the interactive blanks that we have in the table down below. Notice that this table is for prokaryotic and eukaryotic gene expression. The left-hand column contains characteristics of gene expression, the middle column in blue represents the prokaryotes, and the far-right column in green represents the eukaryotes.
When it comes to the requirements for transcription initiation, recall that prokaryotes require what are called sigma factors, whereas eukaryotes do not require sigma factors; instead, they require transcription factors. Both of these are required for transcription initiation to allow RNA polymerase to bind to the DNA and initiate transcription.
Now, next, we have the ribosome size, and recall that prokaryotic organisms use 70S ribosomes. This 70S ribosome consists of a smaller 30S ribosomal subunit and a larger 50S ribosomal subunit. Whereas the eukaryotic ribosome size is going to be an 80S larger ribosome, which consists of a smaller 40S ribosomal subunit and a larger 60S ribosomal subunit.
In terms of the location of transcription and translation, recall that prokaryotic organisms do not have a membrane-bound nucleus. Instead, they have a nucleoid, which is the region that contains the DNA within prokaryotes. This is really where transcription occurs, in the nucleoid. It could also be said that transcription occurs in the cytoplasm.
Recall that with prokaryotes, transcription and translation occur in the same region, and for translation, we could also say the nucleoid or the cytoplasm. Now, in eukaryotes, this is going to be different because eukaryotic organisms contain a membrane-bound nucleus that stores the DNA. Thus, the location of transcription for eukaryotes is the nucleus. Translation in eukaryotic organisms does not occur in the nucleus. Instead, it occurs either in the cytoplasm or the rough endoplasmic reticulum, which I'm going to abbreviate as rough ER or RER.
In terms of having simultaneous transcription and translation, prokaryotes do have simultaneous transcription and translation, so we can say yes to this question. Whereas for eukaryotes, this is not the case; they do not have simultaneous transcription and translation because they occur in different locations.
In terms of requiring mRNA processing, recall that prokaryotic organisms do not process their messenger RNAs. Whereas eukaryotic organisms do tend to process their mRNAs. This processing includes adding a modified guanine cap to the 5' end and a poly-A tail to the 3' end. It also involves removing introns and splicing together exons. Regarding introns and exons, prokaryotes tend not to have introns, whereas eukaryotes do tend to have both introns and exons.
In terms of having either monocistronic or polycistronic mRNA, recall that prokaryotes can have either monocistronic mRNA, which contains only one single gene, or polycistronic mRNA, which contains two or more genes. Eukaryotes tend to only have monocistronic mRNAs that contain a single gene.
This concludes our review of prokaryotic and eukaryotic gene expression. I'll see you all in our next video.
