6. Regulation of Gene expression II

Question 1

What is riboswitch

Answer 1

short sequence of RNA that change thie rconformation upon binding small molecules such as metabolites, usually resides 5’ UTR

• can activate ‘self-cleaving’ ribozyme activity (which activity to break the mRNA)
• cab affact initiation by forming a secondary structure

Question 2

What is a common example of deaminition

Answer 2

A to I/G in RNA duplexes by ADAR (translates into altered amino acid codons)

ADAR binds to secondary structure at intersection of exon and intron

Question 3

When does abnormal mRNA degradation occur

Answer 3

In abnormal splicing where the intron that was not removed has a codon similar to stop codon.

• premature termination of translation leaves beacon EJC
• upF proteins to build up and degradation of mRNA

Question 4

what does 3’ UTR contain

Answer 4

regulatory elements that participate in transcript stability

Question 5

Why is the 5’ end important

Answer 5

• aids mRNA nuclear export
• protect 5’ to 3’ exonuclease degredation in cytoplasm
• targets transcripts to ribosome for translation

Question 6

Why is the poly A tail so important

Answer 6

• participates in termination of transcription
• aids mRNA nuclear export
• protects 3’ to 5’ exonuclease degradation
• targets transcripts to ribosome for translation

Question 7

are mRNAs with longer or shorter poly A tails more likely to be translated

Answer 7

longer

Question 8

What happens if the poly A tail of mRNA is short

Answer 8

degradation occurs:

• PARN binds to exposed 5’ cap (there is no eIF) of nontranslated mRNAs
• to poly A tail deadenylation

Question 9

What is microRNA (miRNA)

Answer 9

small noncoding RNA regulators recognizing 3’ UTRs

• one miRNA recognizes many mRNAs
• more than one miRNA can bind to one mRNA

Question 10

Where do miRNA derive from

Answer 10

from spliced introns in non mammalian species known as mirtons

Question 11

What is RNAi (RNA interference)

Answer 11

is a way of silencing a gene (prevents translation)

Question 12

How does RNAi come into play

Answer 12

• double stranded RNA is cleaved through dicer to form small interfering RNA (siRNA)
• siRNA separate into single stranded RNA
• siRNA bind to complimentary regions of mRNA
• binding causes cleaving/cutting of mRNA
• rest of mRNA is degraded (waste)