BIO315 Molecular Biology Spring 2012

Dr. Henning Schneider

Study Guide T8

Gene Expression II: Post-transcriptional Modifications

1. Splicing I

Concepts:

1. Eukaryotic Genes contain sequence elements that are transcribed but not translated.
2. Introns are removed following transcription of genes.
3. Introns contain conserved recognition sequences at the 5' end, 3' end and the branch point adenine.
4. The splisosome is a large complex composed of snRPs and RNA.
5. The snRPs are positioned on intron exon boundaries and branch point adenines by RNA that is associated with snRPs.

Study Questions:

1. Explain the exon/intron organization of eukaryotic genes.
2. What types of splicing are known?
3. Explain the simple model of splicing.
4. What is a donor, acceptor and branch site in introns?
5. What are the main recognition sequences in the splicing process and where are they located?
6. Explain the electrophoretic behavior of spliced introns. Why do sliced exons migrate faster through a gel?
7. Describe the peculiar behavior of the pre-splicing complex in 4 and 10% PAGE gels.
8. Describe the experiment that was used to determine the branch-point adenine.
9. Describe the organization of a splicosome including the different snRNAs.
10. Explain the formation of the pre-splicing complex.
11. Explain the step-wise process of splicosome formation.
12. Explain the function of U1-U6 snRNAs. Which one of these snRNAs is essential for splicing?
13. Explain how snRNA facilitates the alignment of pre-mRNA in the splicosome.
14. Outline the steps of the experiment that was performed to identify the branchpoint adenine.
15. Explain the term alternative splicing.
16. Explain why splicing can have a dramatic effect on the development of organisms such as Drosophila.
17. Explain how the sex is determined by splicing of genes.
18. Explain the "one gene - one protein" dogma is outdated.
19. Explain the consequences of alternative splicing for the functional organization of genomes.
20. Explain the organization of snRNAs and snRNPs.
21. Explain the interaction of snRNAs U2, U5, and U6.
22. How is U6 snRNP positioned in the 5' region of the intron?
23. How is U1 snRNP positioned in the 5' region of the intron?
24. Explain the rationale of the experiment that located the binding of U5 and U6 in specific sites of the exon-intron boundaries.

2. Polyadenylation and Capping

Concepts:

1. Caps are formed at the 5' end of mRNA.
2. Caps come in different forms.
3. Capping is important for transport of mRNA in eukaryotes.
4. mRNA is polyadenylated at the 3' end.
5. Poly-A tails protect mRNA from degradation.
6. The mechanism of polyadenylation involves polyadenylation recognition sequences and polyA polymerase.

Study Questions:

1. List the different functions of capping.
2. Explain the process of polyadenylation.
3. Explain the process of capping.
4. Explain an experiment that demonstrates the effect of capping and polyadenylation on protein synthesis.
5. What are the functions of capping of mRNA?
6. Describe how nucleotides are attached to the 5' end of a mRNA for capping. Which unusual bond is formed?
7. Explain the effect of capping on RNA stability.
8. Explain the differences between type 0, type 1 and type 2 caps.
9. Explain why capping is important for the transport of mRNA from the nucleus into the cytoplasm.
10. Explain the experiment that was performed to demonstrate the role of capping in mRNA transport or translocation.
11. Characterize the structure of a poly-A tail in mRNA.
12. Which signal sequences are important for accurate polyadenylation?
13. Explain an experiment that demonstrates the importance of polyadenylation signal sequences for polyadenylation.
14. Outline the different steps of the experiment that identified polyadenylation sites.

Last modified on May 10, 2012 by HS.