RNA processing

Question 1

Characteristics of prok- coding region is…? What does the gene sequence equal? What sequence is the ribosmoal binding site?

Answer 1

• coding region is uninterrupted
• gene sequence = AA sequence
• shine dalgarno sequence (ribosomal binding site)

Question 2

Mature mRNA in prok

Answer 2

1. 5’ untranslated region - no coding for AA but affects stability of mRNA and regulates translation
2. protein coding region comprised of codons that specify for AA (start and stop codons)

Question 3

Characteristics of euk

Answer 3

• genes are interrupted by exons and introns
• introns much be removed (RNA splicing) - takes place in nucleus

Question 4

What must we add/remove to euk pre mRNA?

Answer 4

1. 7-methyl guanine cap
2. Poly A tail to 3’ end (effects stability)
3. removal of introns (splicing)

Question 5

Eukaryotic intron splicing - Removal of introns must be….? Where is the intron branch point? Where is mRNA cut? What is intron released as? And what happens to the exons?

Answer 5

• removal of introns must be precise
• intron branch point at A residue
  mRNA is cut at the splice sites, intron is released as a lariat and both exons are spliced together

Question 6

Eukaryotic intron splicing 5’ splice site

Answer 6

GU

Question 7

Eukaryotic intron splicing 3’ splice site

Answer 7

AG

Question 8

What happens if mutation occurs at one of the splice sites in euk splicing?

Answer 8

lariat will still form but joining of the 2 exons won’t occur

Question 9

What are the spliceosomes? 5snRNA’s

Answer 9

U!, 2, 4, 5, 6

Question 10

Alternate processing pathways - multiple 3’ cleavage sites- On what exon does this happen? What does it generate? Will it produce another protein? Depends on what?

Answer 10

On the last exon, generates longer or shorter exons, may or may not produce a different protein (depends if it’s upstream or downstream stop codon)

Question 11

Alternate processing pathways - Alternative splicing - What are used to produce different types of mRNAs? What does this result in?

Answer 11

Alternative exons are used to produce different types of mRNA. This results in different proteins from the same sequence

Question 12

RNA editing

Answer 12

guide RNAs add nucleotides to mRNA that were not encoded by DNA

Question 13

RNA editing - editing of apolipoprotein- what does it use? Results in what codon with respect to what binding?

Answer 13

uses cytidine deaminase (C->U) resulting in a stop codon with respect to lipid binding

Question 14

RNA editing - tRNA modifications - do these make different proteins? What does it remove? What is added? How does it modify bases?

Answer 14

(do not make different proteins) removal of 5’ and 3’ sequence and introns, CCA are added, modifies bases enzymatically

Question 15

RNA editing - ribosomal RNA- what does it help the formation of?

Answer 15

(translation) help in the formation of peptide bonds between AA
- euk = nucleolus
- prok = cytoplasm

Question 16

RNA editing - small RNA molecules - snRNAs: what kind of splicing?

Answer 16

post transcriptional splicing

Question 17

RNA editing - small RNA molecules - snoRNAs- How does it modify? In prok or euk?

Answer 17

enzymatic chemical modifications (euk)

Question 18

RNA editing - small RNA molecules - siRNA/miRNA - in what kind of rna? prok or euk?

Answer 18

single stranded RNA (euk)

Question 19

RNA editing - small RNA molecules - CRISPR

Answer 19

defense (prok)

Question 20

RNA editing - small RNA molecules - long non coding- What does it do to gene expression? Euk or prok? Example?

Answer 20

regulates gene expression (euk) ex. X inactivation in Calico cats

Question 21

DNA regulatory promoter

Answer 21

binds transcription factors the positively or negatively influences transcription