exam 3 (regulatory RNA)

Question 1

What are typical functions of RNA

Answer 1

carrier of genetic information
Structural/catalytic component
Regulation of chromatin structure
Transcription

Question 2

Where was RNA interference discovered

Answer 2

roundworm C. elegans

Question 3

Why are C. elegans used as a model organism

Answer 3

• 50-60% of its genes have counterparts in humans
• worm is transparent
• 3 days to grow
• produce hundreds of descendants
• easy manipulation

Question 4

RNAi silences gene expression in what manner?

Answer 4

sequence-specific manner

Question 5

what 3 hypotheses were formed from C. elegans expressing green fluorescent protein, when they were fed bacterial dsDNA

Answer 5

• dsRNA alters target DNA
• dsRNA inhibits transcription
• dsRNA destabilizes mRNA

Question 6

19% of C. elegans fall within ?

Answer 6

operons, which is highly unusual because they are rare in eukaryotes

Question 7

how does RNAi silence gene expression

Answer 7

post-transcriptional repression:

dsRNA causes substantial reduction in mRNA levels of target gene, making it unstable

Question 8

explain the RNAi silencing process

Answer 8

• double stranded DNA gets processed by a dicer into small interfering RNAs
• siRNAs are placed into RNA induced silencing complexes (RISC)
• siRNA guides RISC to target mRNA and cleaves it

Question 9

function of RNAi

Answer 9

defense mechanism against viral infection, found in most eukaryotes

Question 10

how is RNAi used in lab

Answer 10

tool for studying gene expression, genetics, genomics, and identification of gene phenotype

Question 11

how can dsRNA influence C. elegans

Answer 11

C. elegans eat bacteria, and bacteria can express dsRNA, which can feeding of dsRNA can break down genes of C elegans

Question 12

different organisms respond differently to dsRNA, in what form does dsRNA must be in to influence C. elegans and Drosophilia

Answer 12

LONG dsRNA

Question 13

what happens if long dsRNA is injected into humans?

Answer 13

doesn’tt trigger RNAi, bu activates interferon response, nonspecific immune response that protects cells from pathogens

Question 14

what are miRNAs

Answer 14

short ~22 nt RNA molecules that bind to mRNAs to block their translation or induce their degradation

Question 15

how does miRNA contribute to mRNA destablization

Answer 15

shortens the mRNA poly(A) tails

Question 16

result of miR-96 mutation ?

Answer 16

hereditary progressive hearing loss

Question 17

result of miR-184 mutation ?

Answer 17

hereditary eye disease

Question 18

result of miR-17~92 cluster deletion ?

Answer 18

skeletal and growth defects

Question 19

what is the role of RNAi in fission yeast

Answer 19

influences chromatin structure

Question 20

RNAPII transcribes repeated DNA where?

Answer 20

centromeres

Question 21

how is RNA transcript repeated

Answer 21

RDRP transcribes a strand of RNA

Question 22

what occurs after complementary strand of RNA is formed

Answer 22

they hybridize and are diced to form siRNAs, which mediate H3K9me3, compacting chromatin

Question 23

what is piRNA

Answer 23

another class of small noncoding RNA (slightly bigger than miRNA), the last base is 2’O-methylated, increases piRNA stability

Question 24

function of piRNA

Answer 24

involved in germline

• are antisense to transposons
• interact with piwi proteins to silence transposons

Question 25

why do transposons need to be silenced?

Answer 25

could lead to mutations of important genes that would be passed on to the next generation

Question 26

what are long noncoding RNAs (IncRNAs)

Answer 26

associate with chromatin modifiers and transcription factors to influence gene expression, performed by scaffolding protein-protein interactions

Question 27

what allowed for the discovery of IncRNA

Answer 27

chromatin signature

H3K4me3 + H3K36me3 without associated protein-coding gene

Question 28

explain the XIST IncRNA

Answer 28

transcribed from XIC and recruits protein machinery to establish heterochromatin

Question 29

when IncRNA gets out of the nucleus and enters the cytoplasm, what is its function

Answer 29

they influence mRNA stability and translation, can act as miRNA sponges