16.1-16.3,16.6 | RNA Processing

Question 0

RNase III

Answer 0

(Ribonuclease III)

Critical enzyme that digests dsRNA in bacteria during processing of rRNA and some mRNA

Question 1

Primary transcripts

Answer 1

Newly synthesized RNA transcripts (precursor RNA) that have yet to be enzymatically modified to become functional molecules

Question 2

hnRNA

Answer 2

(heterogeneous nuclear RNA)

The bulk constituent of pre-cursor mRNA (commonly considered synonymous)

Question 3

Keys to Degradation of mRNA

Answer 3

(1) 3’ to 5’
(2) Requires endonuclease
(3) Requires exonuclease
(4) Requires polynucleotide phosphorylase

Question 4

Intron

Answer 4

Non-coding regions of transcript

INTeRrupting codON

Question 5

Exon

Answer 5

Coding regions of transcript

EXpressed codON

Question 6

mRNA coding sequence changes

Answer 6

(1) Alternating splicing [Differential splicing]
(2) Trans-splicing
(3) RNA editing

Question 7

5’-cap

Answer 7

Added during first step of pre-mRNA transcript modification that prevents degradation

Question 8

pre-mRNA Transcript Processing Steps

Answer 8

(1) Addition of cap at 5’ end before transcription is completed
- -adds guanacine at 1st base by 5’:5’ link
- -adds -CH3 at 1st base
- -adds -CH3 at 2nd base

(2) Loading of snRNPs and additional proteins to promote splicing [=removal of introns and joining of exons]
(3) Recognition of poly-adenylation site at 3’ end by 2 proteins which will cleave RNA chain
(4) Alternate splicing
(5) Transplicing
(6) RNA editing

Question 9

Five (5) Categories of Introns

Answer 9

(1) Group I } Self-splicing
(2) Group II } Self-splicing
(3) Spliceosomal } Most common nuc. introns
(4) tRNA Introns
(5) Archael introns

Question 10

Cap-binding Complex (CBC)

Answer 10

A specific complex of proteins that recruits capped mRNAs to the ribosome to initiate translation

Question 11

3’ Poly (A) Tail

Answer 11

80 to 250 ‘A’ residues that serve as a binding site for proteins that protect mRNA from enzymatic destruction

Question 12

poly (A) addition site

Answer 12

Loci where endonuclease cleaves the transcript in the initial steps of adding poly (A) tail

Question 13

RNA splicing

Answer 13

Series of eukaryotic RNA processes that results in mature, translation competent RNA

Question 14

Proteome

Answer 14

The entirety of a cells DNA, RNA and protein

Question 15

Alternative splicing

Answer 15

Process splicing together exons from primary transcript of a gene in various combinations creating new, unique mRNA

Question 16

Splice site

Answer 16

Nucleotide sequences between introns and exons that determine whether the exon will be included in mature mRNA

Question 17

poly(A) site choice

Answer 17

When a complex transcript has more than one site for cleavage and polyadenylation thus the site closest to 5’ is chosen

Question 18

Branch point

Answer 18

Internal ‘A’ residue just upstream from the 3’ splice site

Question 19

Trans-splicing

Answer 19

Process where primary sequence is covalently linked to a separate piece of RNA as introns are removed

Question 20

Retrohoming

Answer 20

A transposition process where the encoded protein forms a complex with the intron RNA after the intron is spliced from the primary transcript

Question 21

RNA Editing

Answer 21

Expansion of genomic coding capacity by creating mRNA not directly encoded by DNA

Question 22

Editosome

Answer 22

Enzyme that catalyzes addition/deletion RNA editing

Question 23

Ribozyme

Answer 23

RNA based enzyme of post-transcriptional processing

Question 24

Adenosine deaminase acting on RNA (ADAR)

Answer 24

RNA editing enzyme that catalyses the conversion of adenosine to inosine