Nucleic Acids and DNA Replication

Question 1

What is a nucleotide?

Answer 1

A monomer that makes up a polynucleotide

Question 2

Give 2 examples of polynucleotides

Answer 2

DNA and RNA

Question 3

What is a DNA nucleotide made up of?

Answer 3

Phosphate, a pentose sugar and a nitrogen containing base

Question 4

What is the pentose sugar in DNA?

Answer 4

deoxyribose

Question 5

What are the nitrogen containing bases in DNA?

Answer 5

Adenine, Thymine, Cytosine and Guanine

Question 6

What does DNA stand for?

Answer 6

Deoxyribonucleic acid

Question 7

How many strands does DNA have?

Answer 7

2

Question 8

What sort of polynucleotide is DNA?

Answer 8

Long

Question 9

What is the role of DNA?

Answer 9

It carries genetic information which codes for proteins

Question 10

Why didn’t scientists believe DNA carried genetic information?

Answer 10

Because of its relatively simple structure

Question 11

In a molecule of DNA how do the strand run?

Answer 11

Antiparallel

Question 12

How are complimentary bases join in DNA?

Answer 12

By hydrogen bonds

Question 13

What is the DNA backbone known as?

Answer 13

The sugar-phosphate backbone

Question 14

How do nucleotides join to form a polynucleotide?

Answer 14

Condensation reaction

Question 15

What bonds form between nucleotides?

Answer 15

Phosphodiester

Question 16

What does A pair with in DNA?

Answer 16

T

Question 17

How many hydrogen bonds form between A-T

Answer 17

2

Question 18

What does C pair with?

Answer 18

G

Question 19

How many hydrogen bonds form between C-G?

Answer 19

3

Question 20

What is different about an RNA nucleotide?

Answer 20

The pentose sugar is Ribose instead of Deoxyribose

Question 21

What can the RNA nitrogen containing bases be?

Answer 21

Adenine, Uracil, Cytosine and Guanine

Question 22

What sort of polynucleotide is RNA?

Answer 22

Short

Question 23

What is the role of RNA?

Answer 23

It transfers genetic code from DNA (in the nucleus) to ribosomes in the cytoplasm

Question 24

What are ribosomes formed from?

Answer 24

RNA and proteins

Question 25

What do ribosomes form?

Answer 25

Proteins

Question 26

In RNA what does A pair with?

Answer 26

U

Question 27

Which enzyme unwinds the DNA double helix?

Answer 27

DNA helicase

Question 28

How does DNA helicase work?

Answer 28

By breaking hydrogen bonds between complimentary bases

Question 29

What happens to both strands once they are separated?

Answer 29

They act as templates

Question 30

What happens to the template strands?

Answer 30

They attract free nucleotides

Question 31

Which enzyme forms phosphodiester bonds?

Answer 31

DNA polymerase

Question 32

How does DNA polymerase work?

Answer 32

It joins free nucleotides by catalysing the condensation reaction that forms phosphodiester bonds

Question 33

Why is DNA replication semi-conservative?

Answer 33

New DNA contains one original strand and one new strand

Question 34

How are the original strand and the new strand joined?

Answer 34

By DNA ligase

Question 35

How do the DNA strands run?

Answer 35

Antiparallel

Question 36

What effect does DNA being antiparallel have on nucleotides?

Answer 36

They are arranged differently

Question 37

In what direction does DNA polymerase travel?

Answer 37

5 prime to 3 prime

Question 38

Why does DNA polymerase travel 5 to 3 prime?

Answer 38

The active site of DNA polymerase has a specific tertiary structure and only substrates with the correct orientation (complimentary orientation) can form an enzyme-substrate complex

Question 39

What happens as a result of DNA polymerase travelling 5 to 3 prime?

Answer 39

One strand is continuously formed and the other is formed in fragments

Question 40

What is the continuously formed strand called?

Answer 40

The leading strand

Question 41

What is the fragmentally formed strand called?

Answer 41

The lagging strand

Question 42

How is the lagging strand formed?

Answer 42

In short fragments which are made as bases are exposed/paired up because of the direction of travel of DNA polymerase

Question 43

What happens to the two strands of DNA after the sugar-phosphate backbone is reformed?

Answer 43

Hydrogen bonds reform between complimentary bases

Question 44

How to free nucleotides attach?

Answer 44

By complimentary base pairing

Question 45

What does semi-conservative DNA replication mean?

Answer 45

New DNA is made up of one original strand and one new strand

Question 46

How can it be proved that DNA replication is semi-conservative?

Answer 46

A population of bacteria are cultured in a growth medium where the only nitrogen available is heavy nitrogen (N15) so that when centrifuged only one (heavy) band is observed. The cells are then transferred to a medium with only light nitrogen (N14). After one replication the DNA strand will be an intermediate containing 1/2 (N14) and 1/2 (N15) and will appear as one band double the width. After two replications in a light nitrogen (N14) environment two intermediate bands (as seen in 1st rep|) will be observed and two light bands which contain only light nitrogen (N14)

Question 47

In which phase of interphase does DNA replication occur?

Answer 47

S1

Question 48

What is the enzyme called which joins the nucleotides together to form a new strand during DNA replication?

Answer 48

DNA Polymerase

Question 49

After the DNA strands have separated during DNA replication, what is attracted to each strand?

Answer 49

Nucleotides