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AQA AS Biology > Nucleic Acids and DNA Replication > Flashcards

Nucleic Acids and DNA Replication Flashcards

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1
Q

What is a nucleotide?

A

A monomer that makes up a polynucleotide

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2
Q

Give 2 examples of polynucleotides

A

DNA and RNA

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3
Q

What is a DNA nucleotide made up of?

A

Phosphate, a pentose sugar and a nitrogen containing base

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4
Q

What is the pentose sugar in DNA?

A

deoxyribose

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5
Q

What are the nitrogen containing bases in DNA?

A

Adenine, Thymine, Cytosine and Guanine

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6
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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7
Q

How many strands does DNA have?

A

2

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8
Q

What sort of polynucleotide is DNA?

A

Long

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9
Q

What is the role of DNA?

A

It carries genetic information which codes for proteins

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10
Q

Why didn’t scientists believe DNA carried genetic information?

A

Because of its relatively simple structure

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11
Q

In a molecule of DNA how do the strand run?

A

Antiparallel

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12
Q

How are complimentary bases join in DNA?

A

By hydrogen bonds

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13
Q

What is the DNA backbone known as?

A

The sugar-phosphate backbone

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14
Q

How do nucleotides join to form a polynucleotide?

A

Condensation reaction

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15
Q

What bonds form between nucleotides?

A

Phosphodiester

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16
Q

What does A pair with in DNA?

A

T

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17
Q

How many hydrogen bonds form between A-T

A

2

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18
Q

What does C pair with?

A

G

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19
Q

How many hydrogen bonds form between C-G?

A

3

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20
Q

What is different about an RNA nucleotide?

A

The pentose sugar is Ribose instead of Deoxyribose

21
Q

What can the RNA nitrogen containing bases be?

A

Adenine, Uracil, Cytosine and Guanine

22
Q

What sort of polynucleotide is RNA?

A

Short

23
Q

What is the role of RNA?

A

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

24
Q

What are ribosomes formed from?

A

RNA and proteins

25
Q

What do ribosomes form?

A

Proteins

26
Q

In RNA what does A pair with?

A

U

27
Q

Which enzyme unwinds the DNA double helix?

A

DNA helicase

28
Q

How does DNA helicase work?

A

By breaking hydrogen bonds between complimentary bases

29
Q

What happens to both strands once they are separated?

A

They act as templates

30
Q

What happens to the template strands?

A

They attract free nucleotides

31
Q

Which enzyme forms phosphodiester bonds?

A

DNA polymerase

32
Q

How does DNA polymerase work?

A

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

33
Q

Why is DNA replication semi-conservative?

A

New DNA contains one original strand and one new strand

34
Q

How are the original strand and the new strand joined?

A

By DNA ligase

35
Q

How do the DNA strands run?

A

Antiparallel

36
Q

What effect does DNA being antiparallel have on nucleotides?

A

They are arranged differently

37
Q

In what direction does DNA polymerase travel?

A

5 prime to 3 prime

38
Q

Why does DNA polymerase travel 5 to 3 prime?

A

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

39
Q

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

A

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

40
Q

What is the continuously formed strand called?

A

The leading strand

41
Q

What is the fragmentally formed strand called?

A

The lagging strand

42
Q

How is the lagging strand formed?

A

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

43
Q

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

A

Hydrogen bonds reform between complimentary bases

44
Q

How to free nucleotides attach?

A

By complimentary base pairing

45
Q

What does semi-conservative DNA replication mean?

A

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

46
Q

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

A

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)

47
Q

In which phase of interphase does DNA replication occur?

A

S1

48
Q

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

A

DNA Polymerase

49
Q

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

A

Nucleotides

AQA AS Biology (18 decks)

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