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Multiple Choice
Which of the following statements about mRNAs in prokaryotes and eukaryotes is true?
A
Both prokaryotic and eukaryotic mRNAs are synthesized in the nucleus.
B
Eukaryotic mRNAs typically have a 5' cap and a poly-A tail, while prokaryotic mRNAs generally lack these modifications.
C
Prokaryotic mRNAs are usually monocistronic, while eukaryotic mRNAs are polycistronic.
D
Eukaryotic mRNAs are immediately translated as they are transcribed, just like in prokaryotes.
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1
Understand the cellular locations where mRNA synthesis occurs: In eukaryotes, transcription happens in the nucleus, while in prokaryotes, which lack a nucleus, transcription occurs in the cytoplasm.
Recall the post-transcriptional modifications typical of eukaryotic mRNAs, such as the addition of a 5' cap and a poly-A tail, which are important for mRNA stability and translation efficiency.
Recognize that prokaryotic mRNAs generally do not have these modifications (5' cap and poly-A tail) because their transcription and translation processes are coupled and occur in the cytoplasm.
Distinguish between monocistronic and polycistronic mRNAs: Eukaryotic mRNAs are usually monocistronic (one gene per mRNA), whereas prokaryotic mRNAs can be polycistronic (multiple genes per mRNA).
Understand the timing of translation relative to transcription: In prokaryotes, translation can begin while mRNA is still being synthesized (coupled transcription-translation), but in eukaryotes, mRNA must be processed and transported out of the nucleus before translation begins.