Unit 1: Human Cells - Key Area 2 - Structure and replication of DNA Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What does DNA consist of?

A

Units called nucleotides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are nucleotides made of?

A

Phosphate, deoxyribose sugar, and a base

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What forms the genetic code?

A

The base sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What holds each strand of DNA together?

A

Each individual strand of DNA is held together by a strong chemical bond between the phosphate of one nucleotide and the carbon 3 of the sugar, on another nucleotide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What holds the bases in adjacent strands together and what does this cause?

A

Weak hydrogen bonds hold the bases together and make them coil into a double helix structure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does the 3’ end of a DNA strand have?

A

A deoxyribose sugar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does the 5’ end of a DNA strand have?

A

A phosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What end can nucleotides only be added to?

A

The 3’ end.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How many different nucleotides are there and what causes them to be different?

A

There are 4 different nucleotides, depending on the base they have.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the 4 different bases?

A

Adenine, Cytosine, Guanine and Thymine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What do the 2 DNA strands have running in different directions?

A

Their phosphate backbone.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the double helix described as having?

A

The Double helix is described as having two anti-parallel chains of nucleotides because one side goes from 5’ to 3’ and the opposite side goes from 3’ to 5’.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is DNA arranged in?

A

Tightly coiled chromosomes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is DNA polymerase and what is its function?

A

DNA polymerase is an enzyme that controls the formation of the sugar-phosphate bonding of the nucleotides into the DNA strand.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a primer?

A

A short sequence of nucleotides at the 3’ end.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What strand has to be replicated in fragments?

A

The lagging strand (5’ end).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the 5’ end also called and why is this?

A

The lagging strand because it has to be replicated in fragments and is slower than the 3’ end.

18
Q

What is the 3’ end also called?

A

The leading strand.

19
Q

What is ligase and what does it do?

A

Ligase is an enzyme that joins all the DNA fragments together once they are all in place.

20
Q

For DNA replication to occur, what must the nucleus contain?

A

Primers, DNA (Template), Enzymes(Ligase and DNA Polyemrase), ATP and Nucleotides (the 4 types).

21
Q

Where does DNA replication occur?

A

In the nucleus.

22
Q

What is the first thing that happens to the DNA molecule in the DNA replication process?

A

A DNA molecule unwinding.

23
Q

What happens to the DNA molecule after it has unwound in DNA replication?

A

The hydrogen bonds between the adjacent bases are broken and these bases act as a template for a new DNA strand to be made.

24
Q

What happens after the nucleotides are exposed in DNA replication?

A

Free-floating nucleotides in the nucleus join on to their complementary bases. This happens simultaneously along the DNA strand.

25
Q

Which end of the DNA can nucleotides be added to?

A

The 3’ end.

26
Q

How do you know which end of a DNA strand is the 5’ end?

A

It is joined to a phosphate.

27
Q

Why is DNA replication important?

A

DNA replication is important so that when cells divide they have to have the correct genetic information they need to function properly and that no information is lost.

28
Q

Why is a primer needed in DNA replication?

A

A primer is needed in DNA replication because DNA polymerase can only add nucleotides to a pre-existing chain.

29
Q

What is the function of the PCR?

A

PCR amplifies DNA. ( It creates many copies of a piece of DNA in vitro).

30
Q

What does the amplification of DNA involve the use of?

A

The amplification of DNA involves the use of primers. Each primer is a short strand of DNA complementary to a specific target sequence at the 3’ end of the strand to be replicated.

31
Q

What are the steps involved in PCR?

A
  • DNA is heated (94–96 °) to separate/denature the DNA stands.
  • It is then cooled (50–65 °C) to allow the primers to bind to the target sequence of DNA.
  • Heat tolerant DNA polymerase at 72 °C then adds nucleotides to the primers (at the 3’ end of the original DNA strands).
  • Repeated cycles of heating and cooling amplify the region of DNA.
  • The first cycle of replication produces 2 identical; DNA molecules, the second produces 4 molecules and so on and in an hour a short length can become a million.
32
Q

What is the first process of PCR called which is carried out at 94 - 96 degrees celsius?

A

Denaturation/separation.

33
Q

What happens in the first stage of PCR?

A

The DNA is heated so it is denatured and the weak hydrogen bonds between the bases are broken to leave two single strands.

34
Q

What is the second process of PCR called where the temperature is cooler at around 68 degrees celsius?

A

Annealing

35
Q

What is the last process of PCR called which is carried out about 72 degrees celsius?

A

Elongation

36
Q

What are the practical uses of PCR?

A
  • Solve crimes - if not enough DNA is found to work on it can be amplified so the forensics people have more to work with (DNA profiling).
  • Diagnosing genetic disorders - testing for cystic fibrosis etc.
  • Settiling paternity disputes using (DNA profiling).
37
Q

What is the role of ligase?

A

Joins fragments of DNA at the 5’ end strand/ lagging strand.

38
Q

What is the role of DNA polymerase?

A

Adds nucleotides to the 3’ end of a strand when there is a pre-existing chain and primer.

39
Q

The 5’ end is replicated in fragments, whilst the 3’ end strand is replicated continuously. Explain why the strands are replicated in different ways?

A

DNA polymerase can only add nucleotides at the 3’ end of a growing strand.

40
Q

What happens to the primers in the second stage of PCR?

A

The primers bind or anell to the target sequence of DNA.

41
Q

Why is the temperature raised again in the third process of PCR?

A

So the temperature is closer to the optimum temperature for DNA polymerase to add nucleotides to the primers.