Seminari 5 - Processament i maduració dels RNAs (2017)Ejercicio Catalán
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Seminari T5 – Processament i maduració dels RNAs
E. R. gèniques
Solucions al qüestionari corresponent al curs 2016/17. Les respostes correctes són les
marcades en color vermell.
1. In a biochemical experiment, you compare the products from splicing reactions carried out in vitro using three different substrates. In each case the substrate is a construct containing a single intron surrounded by two exons, and in all cases the construct is the same overall size. But in one case, the intron is a group I intron, in another a group II intron, and in the third an intron removed by the spliceosome. Each construct is labelled in a manner that allows it to be detected after gel electrophoresis, and each is tested in two reactions--one, conditions that support self-splicing, and two, in the presence of nuclear extract as well. Identify each letter (A, B and C) with the intron type.
A: Intron removed by the spliceosome.
B: Group II intron.
C: Group I intron.
→ “A” és un intró eliminat pel complex de tall i unió (spliceosome) perquè només és processat quan hi ha extractes nuclears.
→ “B” és un intró del grup II perquè és processat sense necessitat d’extracte nuclear (self-splicing), i perquè els productes (exons i llaç d’intró) s’assemblen als de l’intró modificat pel complex de tall i unió (A).
Pàgina 1 → “C” és un intró del grup I perquè és processat sense necessitat d’extracte nuclear (self-splicing), i perquè el producte (un intró) no és un llaç ni s’assembla al de l’intró del complex de tall i unió (A).
En Pere de sa Somera Seminari T5 – Processament i maduració dels RNAs E. R. gèniques 2. The following eukaryotic structural gene contains two introns and three exons. Below there are four possible mRNA products of this gene. Choose the label that explain what may have caused each mRNA: exon 1 – intron 1 – exon 2 – intron 2 - exon 3 exon 1 – exon 2 – exon 3 No mRNA produced exon 1 – exon 2 – intron 2 – exon 3 Mutation in splicing signal sequences in both intron 1 and intron 2 No mutation in any splicing signal Mutation in the gene’s promoter sequence Mutation in a splicing signal sequence in intron 2 3. Sort the following sentences to show the order of events as they are thought to occur during eukaryotic transcription involving RNA polymerase II 1 2 3 4 5 6 7 TFIID binds to the TATA box TFIIB, TFIIF and RNA pol II bind TFIIE and TFIIH bind Synthesis of the pre-mRNA begins at the +1 nucleotide A 5' cap is added to the pre-mRNA Spliceosome complexes carry out intron splicing A poly-A tail is added to the pre-mRNA Pàgina 2 4. Which are the basis of interaction between snRNPs and the pre-mRNA splicing substrate? a. The interaction involves hydrophobic interactions between bases in the premRNA and the complementary bases within the small nuclear RNA (snRNA) component of the snRNP complex.
b. The interaction involves a covalent bond between bases in the pre-mRNA and bases within the small nuclear RNA (snRNA) component of the snRNP complex.
c. The interaction involves hydrogen bonding between bases in the pre-mRNA and the side chains of some amino acids within the protein component of the snRNP complex.
d. The interaction involves hydrogen bonding between bases in the premRNA and the complementary bases within the small nuclear RNA (snRNA) component of the snRNP complex.
En Pere de sa Somera Seminari T5 – Processament i maduració dels RNAs E. R. gèniques 5. If the 5′ splice site sequence changed from 5′-GUAAGU-3′ to 5′GUAUGU-3′, predict the effect of the sequence change on U1 binding and U6 snRNP binding in an in vitro protein-RNA binding assay.
a. The mutation will likely cause a decrease in binding of U1 to the 5' splice site and will likely enhance binding of the U6 snRNP with the 5' splice site.
b. The mutation will likely cause an enhance binding of the U1 and U6 snRNP with the 5' splice site.
c. The mutation will likely cause a decrease in binding of U1 and U6 to the 5' splice site.
d. The mutation will likely cause a decrease in binding of U6 to the 5' splice site and will likely enhance binding of the U1 snRNP with the 5' splice site.
6. In Tetrahymena, group I introns are found in genes for: a. histones b. tRNAs c. snRNAs d. rRNAs e. ribosomal proteins En Pere de sa Somera Pàgina 8. Which of the following is not part of the bacterial degradosome? a. a 3′ to 5′ exonuclease b. Endonucleases c. An enzyme that removes pyrophosphate from the 5' terminus.
d. a 5′ to 3′ exonuclease 3 7. The process of protein splicing is catalyzed by: a. one of the two exteins b. an intron c. snRNPs.
d. a guide RNA e. the intein Seminari T5 – Processament i maduració dels RNAs E. R. gèniques 9. mRNAs that lack an in-frame stop codon are degraded by the process of: a. No-go decay (NGD) b. Nonstop decay (NSD) c. Nonsense-mediated decay (NMD) 10. Some RNA-binding proteins stay bound to transcripts after synthesis and through transport to the cytoplasm.
11. During degradation of a typical eukaryotic mRNA, the removal of the poly(A) tail usually precedes decapping.
12. What base is added to eukaryotic transcript to create the 5' cap? a. G b. C c. T d. U e. A 13. Removal of the 5' cap in a eukaryotic transcript triggers degradation of the mRNA by: a. Endonucleases b. Random degradation from multiple sites in the transcript c. 5’-3’ exonucleases d. 3’-5’ exonucleases En Pere de sa Somera Pàgina 15. Which snRNP binds to the second exon at the 3' splice site and to the first exon to correctly position the exons for splicing? a. U2 b. U5 c. U6 d. U4 e. U1 4 14. Trans-splicing generates what structure in the intermediate? a. Linear molecule b. Y-shaped molecule c. Lariat d. Circle Seminari T5 – Processament i maduració dels RNAs E. R. gèniques 16. U1 snRNA initiates intron splicing by binding to: a. the central part of the first exon b. the 5' splice site of the intron c. the 3' splice site of the intron d. the branch sequence of the intron 17. In RNA editing, the guide RNA: a. Can interact with many different RNAs.
b. Can change a uracil to another base c. Can control the insertion or deletion of uracils d. Must have the same sequence as the end result of the edited RNA 18. Which part of an eukaryotic mRNA can be used to purify it? a. The 5' and 3' splice sites b. The 5' cap c. The exon junction complex (EJC) d. The poly A tail 19. What is the exon junction complex (EJC)? a. It can enhance or suppress splice site selection, depending on where they bind relative to the alternative exon.
b. It is a multimegadalton ribonucleoprotein (RNP) complex comprised of five snRNPs and numerous proteins.
c. It is a protein component of the spliceosome that is not part of one of the snRNPs d. It is a protein complex which forms on a pre-mRNA strand at the junction of two exons which have been joined together during RNA splicing.
Pàgina 5 20. Which molecules form the spliceosome? a. small nuclear RNA (snRNA) b. small nucleolar RNA (snoRNA) c. splicing factors d. small cytoplasmic RNA (scRNA) En Pere de sa Somera ...