Module 8: V1 - V4

Question 1

What is the structure of DNA?

Answer 1

double-helix

Question 2

How does DNA encode information?

Answer 2

the balance between A=T and G=C pairs

Question 3

Which biological processes involve DNA?

Answer 3

transcription, replication, recombination, repair and regulation

Question 4

What biological processes is RNA involved in?

Answer 4

transcription, replication, translation, regulation and viruses

Question 5

Which types of structures does RNA often form?

Answer 5

hairpins and loops

also complex 3D structures such as tRNA

Question 6

What are nucleotides for?

Answer 6

components for RNA and DNA
used for energy storage e.g. ATP
cofactors in metabolism e.g. NAD+ and FAD+

Question 7

Which nucleotides are purines?

Answer 7

nucleotides with a double-ring structure

Question 8

Which nucleotides are pyrimidines?

Answer 8

nucleotides with a single-ring structure

Question 9

What is the 5’ and 3’ end of DNA?

Answer 9

the 5’ end terminates at 5C and the 3’ end terminates at a phosphate group

Question 10

Why is A always paired with T and G always paired with C?

Answer 10

this is because purines must always be matched up with pyrimidines

Question 11

How many hydrogen bonds are there between A and T?

Answer 11

two

Question 12

How many hydrogen bonds are there between G and C?

Answer 12

three

Question 13

When does a cell replicate its DNA?

Answer 13

during the S (DNA synthesis) phase

Question 14

What is DNA synthesised by?

Answer 14

DNA polymerases

Question 15

What is the role of DNA polymerase III?

Answer 15

the main polymerase in DNA replication

Question 16

What is the role of DNA polymerase I?

Answer 16

has functions in repair and recombination too

Question 17

What allows the synthesis reaction of DNA to occur?

Answer 17

coordination of Mg2+ by aspartic acids
Mg2+ ions coordinate phosphate groups
DNA polymerases can only extend at the 3’ end
DNA polymerases need a double stranded section to start

Question 18

Activity of which enzymes occurs in DNA polymerase I?

Answer 18

3’ -> 5’ exonuclease (proofreading) and 5’ -> 3’ exonuclease

Question 19

Activity of which enzyme occurs in DNA polymerase III?

Answer 19

3’ -> 5’ exonuclease (proofreading)

Question 20

What is the DUE section of the oriC sequence rich in?

Answer 20

AT base pairs

Question 21

What is the role of DnaA protein?

Answer 21

recognises ori sequence; opens duplex at specific sites in origin

Question 22

What is the role of DnaB protein (helicase)?

Answer 22

unwinds DNA

Question 23

What is the role of primase (DnaG protein)?

Answer 23

synthesises RNA primers

Question 24

What is the role of single-stranded DNA-binding protein (SSB)?

Answer 24

binds single-stranded DNA

Question 25

What is the role of DNA gyrase (DNA topoisomerase II)?

Answer 25

relieves torsional strain generated by DNA unwinding

Question 26

What are the major differences between RNA and DNA, both in their components and their overall structure?

Answer 26

RNA is ribonucleic acid while DNA is deoxyribonucleic acid as it contains a ribose which lacks one oxygen atom RNA is single stranded while DNA is double stranded RNA has uracil instead of thymine

Question 27

What are nucleotides used for in the cell?

Answer 27

building blocks for the synthesis of DNA and RNA | also messengers and energy moving molecules

Question 28

What would be different about the structure of DNA if the base pairing were between a purine and a purine, and a pyrimidine and a pyrimidine?

Answer 28

since the matching of purines to pyrimidines allows for constant width of DNA to be maintained, if purines were to bind to purines or if pyrimidines were to bind to pyrimidines, the width of DNA would vary

Question 29

Explain how the mechanism of replication of DNA is immediately apparent from its structure.

Answer 29

the structure of DNA is what allows replication to occur as each parent strand is used as a template for the complimentary replicated strand

Question 30

Why is it important that part of the sequence of the origin of replication is AT-rich?

Answer 30

because AT-rich regions of the origin prevent DNA strands from separating due to tension

Question 31

How does a nucleic acid 'recognise' another nucleic acid? We will see this happen in many different processes, but one example would be a nucleotide entering the DNA polymerase during replication, and staying long enough for the phosphate backbone to be polymerised.

Answer 31

the key to recognition of specific nucleic acid sequences is base pairing between complementary strands of RNA or DNA