RNA Structure and Function

Question 1

What are the types of RNA?

Answer 1

Ribosomal RNA (rRNA)
Transfer RNA (tRNA)
Messenger RNA (mRNA)
Noncoding RNA (which edits mRNA to alter gene expression)

Question 2

Prevalence of each RNA type in the cell

Answer 2

80% rRNA
15% tRNA
5% mRNA

Question 3

The start of the RNA molecule is the ____ end and the termination is the ____ end

Answer 3

__5’__
__3’__

Question 4

How are ribosomes formed?

Answer 4

rRNA + Proteins

Question 5

rRNA
Prokaryotic rRNA has ____ different sizes of RNA

Answer 5

3

Question 6

rRNA
Eukaryotic rRNA has ____ different sizes of RNA

Answer 6

4

Question 7

rRNA
Prokaryotic rRNA sizes

Answer 7

23S
16S
5S

Question 8

rRNA
Eukaryotic rRNA sizes

Answer 8

28S
18S
5.8S
5S

Question 9

rRNA
Process of primary transcript conversion to rRNA in eukaryotes

Answer 9

Primary transcript processed into 28S, 18S, 5.8S and 5S rRNAs

Question 10

rRNA
Components of large ribosomal subunit formation in eukaryotes

Answer 10

28S, 5.8S and 5S rRNAs + Ribosomal Protein

Question 11

rRNA
Size of large ribosomal subunit (rRNA and proteins) in eukaryotes

Answer 11

60S

Question 12

rRNA
Process of small ribosomal subunit formation in eukaryotes

Answer 12

18S associates + Ribosomal Proteins

Question 13

rRNA
Size of small ribosomal subunit (rRNA and proteins) in eukaryotes

Answer 13

40S

Question 14

rRNA
Size of Eukaryotic Ribosome

Answer 14

80S

Question 15

tRNA
Characteristics

Answer 15

Exhibit extensive secondary structure
Contain several modified ribonucleotides

Question 16

tRNA
How are modified ribonucleotides formed?

Answer 16

Derived from four normal ribonucleotides

Question 17

tRNA
Names of hairpin-turn loops

Answer 17

TψC Loop
Anticodon Loop
D Loop

Question 18

tRNA
Modified bases of the D loop

Answer 18

Methylated Cytosine
Dihydrouridine

Question 19

tRNA
Function of the anticodon loop

Answer 19

Recognition of complementary mRNA codons

Question 20

tRNA
Modified bases of the TψC loop

Answer 20

Pseudouridine (ψ)

Question 21

tRNA
Structure of Acceptor Stem

Answer 21

5’ - … CCA-3’

Question 22

tRNA
Function of Acceptor Stem

Answer 22

Ester bond forms between 3’-OH group of Adenosine of tRNA and carboxyl group of amino acid

Question 23

mRNA
Difference in prokaryotic and eukaryotic mRNA processes

Answer 23

Compartmentalization of transcription and translation
Protection at their 5’ and 3’ ends
Processing of mRNAs
Prokaryotic mRNAs are polycistronic and eukaryotic mRNAs are monocistronic

Question 24

mRNA
Compartmentalization of transcription and translation in prokaryotes and eukaryotes

Answer 24

Prokaryotes synthesize RNA and proteins in cytoplasm
Eukaryotes separate transcription and translation in nucleus and cytoplasm

Question 25

**mRNA** Protection at the 5' and 3' ends of eukaryotes

Answer 25

Eukaryotic mRNA have 5' cap and 3' poly(A) tail

Question 26

**mRNA** Processing of mRNA in prokaryotes and eukaryotes

Answer 26

Prokaryotic mRNA is not processed Eukaryotic mRNA has introns which are spliced out

Question 27

**mRNA** Monocistronic vs Polycistronic

Answer 27

**Prokaryotes have Polycistronic mRNA** (multiple proteins from one mRNA) **Eukaryotes have Monocistronic mRNA** (one protein formed from each mRNA)

Question 28

**Noncoding RNA** Types

Answer 28

lncRNAs miRNAs siRNAs

Question 29

**Noncoding RNA: lncRNA** Length

Answer 29

>200 nucleotides long

Question 30

**Noncoding RNA: lncRNA** Function

Answer 30

**Affects gene regulation** by binding to DNA, RNA and proteins **Mediates developmental inactivation** of duplicated X chromosomes

Question 31

**Noncoding RNA: miRNAs** Length

Answer 31

21-25 nucleotides

Question 32

**Noncoding RNA: miRNA** Formation

Answer 32

Pri-miRNAs transcribed by RNA Polymerase II from noncoding genome segment

Question 33

**Noncoding RNA: miRNA** Function

Answer 33

Loaded into silencing complex which scans and cleaves mRNA

Question 34

**Noncoding RNA: miRNA** Why is mRNA cleaved by miRNA?

Answer 34

To downregulate gene expression

Question 35

**Noncoding RNA: siRNA** Formation

Answer 35

Processed from double-stranded RNAs in the cytoplasm

Question 36

**Noncoding RNA: siRNA** Origin of double stranded RNA in cytoplasm

Answer 36

Viral RNAs Part of innate cellular immunity

Question 37

**Noncoding RNA: siRNA** Purpose of siRNA

Answer 37

RNA intereference (RNAi)

Question 38

**Noncoding RNA: siRNA** What is RNA interference?

Answer 38

siRNA binds to the mRNA to stop translation

Question 39

What are ribozymes?

Answer 39

RNA molecules acting as enzymes

Question 40

Example of ribozymes

Answer 40

Large ribosomal subunit (23S in prokaryotes and 28S in eukaryotes) Ribonuclease P (essential endonuclease) Spliceosome (converts primary transcript to mature mRNA) Introns