Question

1. In the spliceosome the major ribonuclear proteins that function in splicing are called ________________.

2. Group I and II introns are different from the regular spliceosome because they are ____________________________.

3. What is the purpose of the SR proteins?

4. Many pre-mRNA are alternatively spliced, what does this mean?

5. Some RNAs are edited after they are spliced. How is this accomplished?

Answer 1

1. Ribonucleoproteins are RNA-protein complexes that combine with unmodified pre-mRNA and various other proteins to form a spliceosome,

2. The spliceosome is a complex small nuclear (sn)RNA–protein machine that removes introns from pre-mRNAs via two successive phosphoryl transfer reactions.

But Group I and group II introns are two types of RNA enzymes, ribozymes, that catalyze their own splicing by different mechanisms.

3. SR proteins function as general activators of exon definition by binding cis-elements in pre-mRNA, known as exonic-splicing enhancer elements (ESEs), and thereby facilitate recruitment and/or stabilization of components of the core spliceosome.

4. Alternative splicing is a regulatory mechanism by which exons are joined and introns are removed. This exon binding process is totally random. That's why it's called alternative splicing.

5. RNA editing refers to the process in which the information contained within the RNA is altered by virtue of a chemical change in the base makeup. This is done by changes in specific nucleotides of the RNA.