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Post-Transcriptional RNA Processing

Problems

The 5' Cap and the Poly A Tail

Overview of Post-Transcriptional RNA Splicing

Problem : What are the three post-transcriptional modifications that occur in eukaryotes?

The three post-transcriptional modifications are: 5' capping, poly A tail addition, and splicing.

Problem : What is the function of the 5' cap in eukaryotes?

The 5' cap helps in eukaryotic mRNA recognition by ribosomes during translation.

Problem : What is unique about the linkage that forms the 5' cap and is different from other linkages we have seen?

The 5' cap is formed by a 5'-5' linkage between the 5' end of the primary RNA transcript and the 5' end of the GTP molecule. Previously, we had only seen 5'-3' linkages.

Problem : What is the name of the enzyme that catalyzes the addition of the poly A tail and how does it know where to begin adding As?

Poly (A) polymerase catalyzes the addition of As to the 3' end of a primary RNA transcript. It recognizes the sequence AAUAAA as the site to begin addition.

Problem : The modifications discussed in this section pertain to eukaryotic primary RNA transcripts. Is prokaryotic newly synthesized RNA similarly processed after transcription?

Newly synthesized prokaryotic RNA does not undergo addition of either the 5' cap or the poly A tail or any similar modification.

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