Why is a cap added to mRNA, but not to tRNA or rRNA? A-Transfer RNA and rRNA exhibit complex structures with double stranded regions. The three-dimensional shapes of these molecules keep the 5/' end of the RNA away from the enzymes that process the cap. B-Transcription and processing of mRNA occur in the nucleus, where cap binding proteins are found. These proteins, which add and modify the cap, are not found in the cytoplasm, where tRNA and rRNA are transcribed and processed. C-Each of the three types of RNA are transcribed by different RNA polymerases. Only RNA polymerase II, involved in mRNA synthesis, contains a domain capable of interacting with enzymes that form the cap. D-Only mRNA contains introns. Capping occurs simultaneously with intron removal because the same enzymes and proteins involved in both of these processes must bind to RNA at the same time.

Question

Matteo Baxter

Biology

27 June, 10:47

Why is a cap added to mRNA, but not to tRNA or rRNA? A-Transfer RNA and rRNA exhibit complex structures with double stranded regions. The three-dimensional shapes of these molecules keep the 5/' end of the RNA away from the enzymes that process the cap. B-Transcription and processing of mRNA occur in the nucleus, where cap binding proteins are found. These proteins, which add and modify the cap, are not found in the cytoplasm, where tRNA and rRNA are transcribed and processed. C-Each of the three types of RNA are transcribed by different RNA polymerases. Only RNA polymerase II, involved in mRNA synthesis, contains a domain capable of interacting with enzymes that form the cap. D-Only mRNA contains introns. Capping occurs simultaneously with intron removal because the same enzymes and proteins involved in both of these processes must bind to RNA at the same time.

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Marcos Olson · Answer 1

The correct option is C ' Each of the three types of RNA are transcribed by different RNA polymerases. Only RNA polymerase II, involved in mRNA synthesis, contains a domain capable of interacting with enzymes that form the cap.'

Explanation:

All the different type of RNA's undergo the process of transcription. However, their transcription is carried on by different types of RNA polymerases.

The transcription of the mRNA is carried by RNA polymerase II. The process of capping is essential so that the mRNA is stopped from degradation.

The rRNA is transcribed by RNA polymerase I which cannot add a cap tothe RNA.

The tRNA is transcribed by the RNA polymerase II, but the domain is different which cannot undergo the process of capping.