MCB 250 Lecture Notes - Lecture 30: Alternative Splicing, Phosphodiester Bond, Spliceosome

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viridianfrog129

9 Jan 2020

School

University of Illinois

Department

Molecular and Cell Biology

Course

MCB 250

Professor

J Slauch

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Document Summary

A new phosphodiester bond is formed joining the ends of the two exons: both reactions are catalyzed by a molecular machine called the spliceosome. Alternative splicing: many eukaryotic gene products undergo alternative splicing, i. e. two or more different patterns of exon usage. Splice repressor proteins direct the spliceosome away from a potential splice site. If a gene is transcribed from multiple promoters, it will produce multiple isoforms with different 5" exons. These splice activator proteins attract the spliceosome to. Exon 4, causing it to be included in the female isoform of. Dsx protein: male development, in males, there is no expression of the functional (female) Sxl protein: rather, the spliceosome includes a male-specific exon in the. This male-specific exon contains an in-frame stop codon. Hence, females make twice as much activator, and are able to transcribe from the pe promoter.

Related Questions

Which of the following statements about splicing is false?

A. a single gene can code for many types of protein due to alternative splicing

B. The 5' and 3' regions of the intron are highly variable in sequence

C. the spliceosome is found in the nucleus of the cell

D. The mRNA is composed of exons; introns are spliced out

salmonlocust980

QUESTION 1

Which of the following statements regarding splicing is FALSE?

A) The length of introns determines the efficiency of splicing.

B) Many human neurological disorders are caused by splicing errors and/or mutations in splicing factors.

C) Splicing requires the action of a variety of snRNAs that direct the transesterification reactions.

D) Splicing is dictated by sequence features in pre-mRNA transcripts

QUESTION 2

Which of the following mRNA processing factors does NOT associate with the CTD of RNA polymerase II?

A) splicing factors

B) polyadenylation factors

C) miRNAs/siRNAs

D) capping proteins

QUESTION 3

Which of the following statements about mRNA stability is FALSE?

A) Deadenylation-independent mRNA decay is exclusively in the 5' to 3' direction.

B) The most common pathway of mRNA decay is deadenylation-dependent.

C) Yeast mRNA decay occurs primarily in the 5' to 3' direction, while 3' to 5' decay is more common in mammalian cells.

D) Decapping enzymes are required for all pathways of mRNA decay.

QUESTION 4

You obtain the sequence of a gene containing 10 exons, 9 introns, and a 3â² UTR containing a polyadenylation consensus sequence. The fifth exon also contains a polyadenylation site. To test whether both polyadenylation sites are used, you isolate mRNA and find a longer transcript from muscle tissue and a shorter transcript from all other tissues. Which of the following is the most likely mechanism underlying these alternative transcripts?

A) The fifth exon is spliced out of the mature mRNA transcript in muscle cells.

B) Muscle cells have less effective polyadenylation than other tissues.

C) An alternative CPSF protein is expressed in muscle cells with lower affinity for the polyadenylation sequence in exon 5.

D) The mRNA in muscle cells is edited to eliminate the polyadenylation sequence in exon 5.

blushdonkey474

1. Pre-messenger RNA processing

a. What are the major steps of pre-mRNA processing?

b. How is a cap added to the 5â-end of mRNAs? What is that cap? Can you explain some functions of the cap?

c. What processing happens at the 3â-end of eukaryotic mRNAs? What enzyme is responsible for this? Can you explain some functions of this processing?

d. What is RNA editing? Are you prepared to identify how a single site of editing could change the expression of an mRNA?

e. What are the catalytic sites within an intron? How are they recognized by the spliceosome (you do not have to memorize exact interactions, just understand generally how this occurs)?

f. What is the mechanism of catalysis carried out by the spliceosome? How is this similar to Group I and Group II introns?

g. Are you prepared to answer questions about how splicing defects may result in non-functional protein products?

h. What is alternative splicing and how can it increase the size of the proteome?

emeraldcrocodile431

MCB 250 Lecture Notes - Lecture 30: Alternative Splicing, Phosphodiester Bond, Spliceosome

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