10. Transcription

Which of the following is NOT a method of mRNA modification?

The spliceosome is made up of which of the following components?

Which of the following is not a sequence that the spliceosome recognizes?

After transcription the RNA sequence cannot be changed or modified before translation.

Answer these questions concerning promoters. What role do promoters play in transcription?

A short RNA molecule was isolated that demonstrated a hyperchromic shift, indicating secondary structure. Its sequence was determined to be

5'-AGGCGCCGACUCUACU-3'

Propose a two-dimensional model for this molecule.

Present an overview of various forms of posttranscriptional RNA processing in eukaryotes. For each, provide an example.

One form of posttranscriptional modification of most eukaryotic pre-mRNAs is the addition of a poly-A sequence at the 3' end. The absence of a poly-A sequence leads to rapid degradation of the transcript. Poly-A sequences of various lengths are also added to many bacterial RNA transcripts where, instead of promoting stability, they enhance degradation. In both cases, RNA secondary structures, stabilizing proteins, or degrading enzymes interact with poly-A sequences. Considering the activities of RNAs, what might be general functions of 3'-polyadenylation?