RR9

Question 1

What are the two transesterifications in intron splicing?

Answer 1

1) Cutting at the 5’ end of intron (OH group atttacks the 5’ phosphate)
2) Cutting at the 3’ end of the intron: exon 1 attacks sections of exon 2 still attached to intron

Question 2

Describe tRNA processing

Answer 2

Going from pre-tRNA to mature tRNA
pretRNA transcribed by RNA pol III
1) 5’ end sequence is removed
2) Short segment is removed from tRNA loop
3) CCA is added on 3’ end for quality control
4) There is extensive modification of internal bases

Question 3

What is RRM

Answer 3

A splicing reaction protein
The RNA recognition motif
It fold up structures with Beta sheets, giving it a positive charge

Question 4

What is PTB?

Answer 4

Polypyrimidine tract binding protein
- small RNA binding molecule that aids in splicing

Question 5

What is U2AF?

Answer 5

Protein component that defines the 3’ splice site; helps with splicing efficiency

Question 6

What are SR proteins?

Answer 6

RNA binding proteins with RRM domains and protein:protein interaction domains
Aids in binding of splicing sequences to exons (U1 snRNP and U2snRNP)

Question 7

What is the Cross-exon recognition complex?

Answer 7

SR protein: protein/snRNA

Question 8

What is alternative splicing?

Answer 8

Splicing of pre-mRNA can happen in different ways, giving rise to different proteins. This allows higher DNA/gene complexity

Question 9

Explain alternative splicing and the Sxl in drosophila

Answer 9

Drosophila flies have sexual dimorphism
- Sxl is expressed in females but not in males - why?
- there is a “late” sxl promoter that allows the expression of sxl. This promoter is alternatively spliced, with only females having it, this is why females express the sxl gene.

Question 10

What is the TRA protein? Why is it important

Answer 10

It is a protein females have, differentiating them from males
THey bind exonic facotrs differently.
- Female splice out exon 1 and 3 (makes Tra protein), while males have 2,3,4.

Question 11

RNA editing - what is it?

Answer 11

Mature mRNA sequence is often different from the sequence of the coding region of genomic DNA
- This shows that RNA editing is widespread in mitochondria and plastids
- We often see deamination reactions

Question 12

What is the role of apolipoprotein B

Answer 12

Involved in transformation and movement of cholesterol. Gene product that gives rise to this is in the liver and the gut.
It is different forms in liver and gut
- Large in liver
- Small in intestine - RNA editing

Question 13

How does polyadenylation take place?

Answer 13

PolyA polymerase has 12 A residues added to the 3’ end
- Structure is recognized by PABN1 (polyA binding protein), which catalyzes addition of ~200 A residues