The RNA World

Question 1

The RNA World

Answer 1

Hypothetical stage in the evolutionary history of life on Earth, in which self-replicating RNA molecules proliferated before the evolution of DNA and proteins

Question 2

Originally a

Answer 2

‘Fantasy world’

Question 3

When was the RNA world?

Answer 3

~3.8bn years ago

Question 4

Electronegativity

Answer 4

Ability to attract shared electrons

Question 5

What is electronegativity determined by?

Answer 5

• atomic number
• distance of the valency shell

Question 6

In what direction are the phosphodiester bonds in RNA

Answer 6

5’-3’

Question 7

What is the direction of RNA synthesis

Answer 7

5’OH -> 3’OH

Question 8

Purines

Answer 8

Guanine
Adenine

Question 9

Pyrimidines

Answer 9

Uracil
Cytosine
Thymine

Question 10

Pyrimidines are

Answer 10

CUTe

Question 11

Why can RNA fold?

Answer 11

Due to free 2’OH

Question 12

Examples of RNA folding

Answer 12

1. Duplex
2. Hairpin
3. 90 degree kink
4. Kissing loops
5. Open 3 way junction
6. Open 4 wag junction
7. Stacked 3 way junction
8. 3 way loops

Question 13

Describe the tertiary structure of tRNA

Answer 13

• base pairing between loops folds clover into L shape
• stems stack onto each other
• impaired bases interact with each other
• variable loop induces flexibility and conformational changes

Question 14

What is tertiary structure?

Answer 14

Folding pattern

Question 15

A molecule defines life if it can

Answer 15

1) store information
2) adapt/mutate (evolve)
3) sense the environment
4) catalyse reactions
5) replicate itself

Question 16

RNA can sense

Answer 16

• ions
• temperature
• pH
• salt concentrations

Question 17

Riboswitches are common in

Answer 17

mRNAs of prokaryotes and eukaryotes

Question 18

Hammerhead ribozymes can cleave

Answer 18

Specific RNA sequences

Question 19

Where are ribozymes common

Answer 19

• viruses
• introns
• transposons
• all organisms

Question 20

Other RNA catalysts except ribozymes

Answer 20

• RNA-based ligases
• RNA-based polymerases

Question 21

Problem with RNA World theory

Answer 21

No RNA replicase has been created yet

Question 22

The best RNA replicase we have so far is

Answer 22

A ligase that links its own precursor RNAs

Question 23

Polarised bonds that have a hydrogen are a

Answer 23

Potential hydrogen donor

Question 24

Polarised bonds that are negatively charged are a potential

Answer 24

Hydrogen acceptor