Other RNAs

Question 1

What does short nuclear RNA (snRNA) do? Where is it located?

Answer 1

• It is involved in RNA processing in nucleus, specifically RNA splicing.
• Mostly in nucleus, some in cytoplasm

Question 2

What is small nucleolar RNA (snoRNA)? Where is it located?

Answer 2

• It is involved in the processing and modification of rRNA, tRNA and snRNA
• It is in nucleolus

Question 3

What is a riboswitch?

Answer 3

An RNA DOMAIN that contains a sequence that can change in secondary structure to control its activity. Change in structure is mediated by small molecules.

Question 4

What is a ribozyme?

Answer 4

RNA molecules that display catalytic activity (ex: self-splicing introns, hammerhead ribozymes that are involved in cleavage of RNA)

Question 5

Long Non-Coding RNAs (lncRNAs)

• How long are they?
• Transcribed by?
• What parts of the genetic sequences that code for these RNAs are conserved?
• What are its functions?

Answer 5

• >200 nucleotides
• RNA Pol II or RNA Pol III
• Promoters are well conserved, actual sequence is not –> high degree of diversity and evolution
• Functions
  
  • Activation
  • Structural
  • Repression

Question 6

What is RNAi?

Answer 6

Process by which miRNAs and siRNAs induce silencing

Question 7

miRNA

• Where do these originate from?
• Describe the process of miRNA action

Answer 7

• They are endogenous, so there are genes within the cell’s genome that code for the production of miRNA
• Nucleus: Genes encoding for pri-miRNA are transcribed, pri-miRNA is made and forms hairpin secondary structure. Curly ends of hairpin are removed and pri-miRNA is exported out of nucleus. Cytoplasm: Circular part of hairpin is removed and strands of miRNA are separted. One strand then binds to mRNA complement to silence or degrade the mRNA. The more the miRNA is able to pair with the mRNA the higher the chance of the mRNA being degraded.

Question 8

Why would one argue genes that code for pre-miRNA are polycistronic?

Answer 8

B/c a single pre-miRNA can encode for multiple miRNAs

Question 9

siRNA

• Where does it arise from?
• What is its function?
• Describe its biogenesis pathway.

Answer 9

• Can come from repetitive sequences in the endogenous genome or from exogenous sources, such as viruses
• It’s function is to inhibit viruses, gene expression, and transposomes
• Works through a similar mechanism as miRNA to identify either RNA or DNA and repress or degrade it

Question 10

What is shRNA?

Answer 10

Created by people (or I suppose viruses/bacteria…). A gene is inserted into a plasmid and the gene codes for shRNA. When that plasmid is introduced into the host genome, the gene is transcribed by the cell to produce shRNA, which is then exported out of the nucleus. It is processed in a similar manner as miRNA and has similar functions, the difference being that miRNA is produced by the host and shRNA is not, it is programmed insertion into the host genome that results in the production of RNA.

Question 11

What is morpholino?

Answer 11

A type of siRNA that has been made by people with a modified backbone that makes it more stable and less susceptible to degradation. This molecule does not require gene expression to be active.

Question 12

What is a piwiRNA?

Answer 12

Only in metazoas. They inhibit retrotransposomes, preserve gene integrity and chromosome structure.