Epigenetics III

Question 1

Non-Coding RNAs

Answer 1

do not code for protein
- short vs long (>200nts)

Question 2

snoRNAs

Answer 2

small nucleolar RNA
- post-transcriptional modification *splicing
- encoded in introns

Question 3

snRNAs

Answer 3

small nuclear RNA
- catalyze splicing of pre-mRNA (excise introns)
- associated with snRNPS in Cajal bodies

Question 4

piRNA and exRNA

Answer 4

piwi-interacting RNA
- transposon silencing = stabilize genome

extracellular RNA
- cell communication

Question 5

miRNA vs siRNA

Answer 5

miRNA
- single-stranded + bind to 3’UTR
- target hundreds of mRNA
- regulate genes other than ones that expressed them
- inhibit translation of mRNA
- therapeutic use

siRNA
- double stranded
- knock down specific genes
- regulate same genes that expressed them
- cleave mRNA (silence gene)
- laboratory tool to knock down

Question 6

Pathway of miRNA and siRNA

Answer 6

• dsRNA or mRNA cleaved by DICER = siRNA/miRNA
• RISC targets complementary strand + rids passenger
• AGO recognizes mRNA
  — 1-4 = miRNA
  — 2 = siRNA
• siRNA = complementary guide-target = mRNA cleave
• miRNA = non-complementary guide-target = repress translation

Question 7

Long Non-Coding RNAs

Answer 7

• regulate expression of adjacent protein-coding genes
  gene1 lncRNA gene 2 (prevent expression of 1+2)
• Barr body = inactivate X chromosome