Non Coding RNAs

Question 1

what are the different types of non-coding RNAs which are transcribed called

Answer 1

tRNAs, rRNAs, snoRNAs, lncRNAs and microRNAS

Question 2

what process are microRNAs involved in

Answer 2

gene regulation

Question 3

how do microRNAs regulate genes?

Answer 3

microRNA genes are transcribed to form pre-miRNA which is processed in cytoplasm and cleaved by Dicer into 20-22 nt lengths. these are then recognised by RISC complex and act as a template for other mRNA through base pairing and binding of the 3”UTR. perfect base pairing leads to rapid degradation of mRNA. mismatching bases leads to disregulation of translation- can target multiple genes

Question 4

what is the effect of creating a Dicer KO

Answer 4

embryonically lethal

Question 5

what is the effect of the addition of TLR2 and TLR4 signalling on miRNA

Answer 5

increases miRNA levels, in particular miR-155 which leads to monocyte proliferation and activation

Question 6

give an example of viral genes which are targeted by by host miRNA

Answer 6

HCV genes

Question 7

give 2 examples of viral miRNAs which interfere with the host genes

Answer 7

KSHV miRNA represses the ICAM gene (neutrophil adhesion) and HCMV produces miR-UL112 which down regulates NK cells through MICB

Question 8

what length are lncRNAs

Answer 8

over 200 base pairs

Question 9

give 2 examples of lncRNA

Answer 9

Xist and Hotair

Question 10

during immunological challenges, what happens to the lncRNA Lethe

Answer 10

it is unregulated by TNFa and binds to the ReIA subunit which prevents NFkB binding to targets and releasing pro inflammatory cytokines

Question 11

describe a mechanism by which some lncRNAs down regulate gene expression

Answer 11

act as antisense to form dsRNA preventing translation

Question 12

how do plants and fungi and invertebrates utilise siRNA to protect against viral infection

Answer 12

siRNA derived from viruses is used to degrade viral RNA via a RISC dependent mechanism

Question 13

how do we use siRNA to provide bacterial immunity

Answer 13

can incorporate phage DNA to produce siRNA against that phage

Question 14

what are transposons

Answer 14

mobile fragments of DNA which can move by either a cut/copy and paste mechanism

Question 15

what are class 1 transposons

Answer 15

retrotransposons which were DNA copied to RNA then copied back to DNA and inserted elsewhere in genome, often used by retroviruses. this is the copy and paste mechanism

Question 16

what are class 2 transposons

Answer 16

DNA transposons which move via cut and paste mechanism and so are non-replicative

Question 17

give 2 examples of diseases linked with transponson

Answer 17

haemophilia and X-linked SCID

Question 18

how do piwi RNAs (piRNA) protect against transposon replication/expansion

Answer 18

clusters of transposons are usually found in heterochromatin areas of genes so are not expressed however during development parts of these are transcribed to form piRNAs which can target selfish DNA transposon elements elsewhere in the genome