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IMS > Nucleic Acids and DNA Replication > Flashcards

Nucleic Acids and DNA Replication Flashcards

1
Q

What are the 3 Components of DNA & RNA?

A

Nitrogenous Base
Pentose Sugar
Phosphate group

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2
Q

What are the Nitrogenous bases in DNA/RNA?

A

Pyrimidine - CTU

Purine - GA

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3
Q

What does the Phosphate group do?

A

Act as a bridge between adjacent ribose/deoxyribose groups

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4
Q

What does ATP consist of?

A

3 phosphate groups, ribose and adenine

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5
Q

How is a DNA helix held together by?

A

Base Pairing
C with G
T with A

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6
Q

When does A-U bonding (RNA) occur?

A

Transcription

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7
Q

What is the Structural feature of a DNA double helix?

A

Hydrophobic in centre away from water and Hydrophilic on the outer

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8
Q

How are Hydrophobic bases in DNA stabilised?

A

H-bonding between bases on complimentary strands

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9
Q

How are Hydrophilic bases in DNA stabilised?

A

Sugar-phosphate backbone stabilised by electrostatic and H-bonding with water

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10
Q

What kind of Interactions to stacked bases have?

A

Weak transient electrostatic interactions (van der waals)

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11
Q

What are RNA structural features?

A

Single-stranded RNA adopt secondary structures through base pairing

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12
Q

What is the difference between nucleotides in DNA/RNA polymers?

A

Base on individual units

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13
Q

What is the Polymer described by?

A

Sequence and number of bases

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14
Q

What are nucleic acids defined by?

A

Size and direction

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15
Q

Where are Nucleotides always added in a polynucleotide chain?

A

3’- end

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16
Q

How is a 3’-5’ phosphodiester bond formed?

A

a-phosphate of new nucleotide reacts with 3’-OH group of polymer

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17
Q

What direction does the chain grow?

A

5’-3’ direction. always

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18
Q

What is always at the start of a Nucleic acid chain?

A

5’ Phosphate at the start and terminates with a 3’ OH

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19
Q

Where is DNA in a Eukaryotic cell?

A

Nucleus and helps to compact

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20
Q

What is Chromatin?

A

Histone-bound DNA

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21
Q

What is a Nucleosome?

A

Basic unit of compacted DNA

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22
Q

What is the Core particle of a Nucleosome consist of?

A

Octamer with 2 copies of 4 Histone proteins (H2A,H2B,H3,H4)

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23
Q

What does core DNA consist of?

A

146 BP which wraps around histone core

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24
Q

What does a Chromosome contain during replication?

A

2 chromatids linked by a centromere

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25
What does each Chromatid contain?
1 single DNA molecule compacted as chromatosomes
26
At what phase during Cell cycle does DNA replication take place?
S phase of Interphase
27
What is DNA replication vital for?
Cell growth, Repair, Reproduction
28
What is the model used for DNA replication
Semiconservative model - parent strand seperated creating 2 single strands, each strands used as template for complimentary strand
29
When given a DNA sequence, how would you work out the complimentary strand?
Work out the opposite pairs and then write it backwards for e.g 5'-AGTCT-3' compliment is 3'-TCAGA-5' Written as 5'-AGACT-3'
30
What is the 1st step to DNA replication?
Replication Fork Formation
31
How is the replication fork formed?
Double strand DNA unzip into 2 single strands, the strands form a Y shaped replication fork used as a template
32
How are DNA double strands split into 2 single strands?
Base pairs broken by DNA helicase
33
What direction can DNA only replicate from?
5'-3' Direction
34
What direction is the Replication fork?
Bi-directional
35
What strand orientation forms the Leading strand?
3' to 5' direction
36
What strand orientation forms the Lagging strand?
5' to 3' direction
37
What is Step 2 of DNA replication?
RNA primer binding
38
How does RNA bind to this fork?
Short piece of primer (RNA) binds to 3'end of strand
39
How is the Primer generated?
by DNA primase
40
What is Step 3 of DNA replication?
Elongation
41
How does Elongation occur during cell replication?
DNA polymerase alpha binds to the strand at the site of the primer and adds new comp base pairs during replication
42
After 20 base pairs of replication, what is Elongation taken over by?
DNA pol e (epsilon)
43
What does DNA pol e and gamma do?
Proofreading of 3'5' exonuclease activity
44
Why does DNA pol carry out exonuclease activity?
Prevent incorporation of incorrect nucleotides
45
What does Elongation and DNA pol result in?
Synthesis of 1 continuous replicated DNA strand in the 5'-3' direction
46
How does DNA replication in the Lagging strand?
Multiple RNA primers needed, DNA pol gamma generate comp DNA okazaki fragments to strand between RNA primers
47
What does Replication in Lagging strand do?
Discontinues as new fragments are not joined
48
What is Step 4 of DNA replication in both strands?
Termination
49
How does Termination occur in DNA replication?
RNA primers degraded and filled by action of RNAse H and DNA POL gamma
50
What component of DNA joins any breaks in both strands?
DNA ligase
51
What does DNA ligase do?
Joins any breaks to generate continuous double stranded DNA
52
What is a Genome?
Total DNA in a cell (replicates in 8 hours)
53
Where can DNA replication occur?
At mutiple sites with multiple origins of replication with forks in opposite directions (replication bubbles)
54
What happens with the Inheritance of histones after replication?
Histones are removed in front of the replication bubble
55
What happens to Histones 3 &4?
H3/4 remain intact adjacent to DNA after synthesis - New H3/4 cores bind followed by H2A&B
56
What is Epigenetics?
Heritable changes in phenotype cell behaviour or gene expression causes by changes in DNA base that control activity of genes
57
What are 2 examples of Epigenetics?
Histone modifications - acetylation of Lys | DNA modificationa - methylation of cytosine
58
What does Epigenetic modifications alter?
Chromatin structure to control accessibility of transcription factors
59
What can Epigenetic marks be altered by?
Enviromental stimuli such as smoking and nutrition
60
What did the Dutch Famine 1944 show in Epigenetics?
First date to show early life enviromental coniditions can cause epigenetic changes that persis through life
61
What are 3 Applications of DNA replication?
PCR , DNA sequencing, Precision medicine
62
What is the Definition of Precision medicine?
Influence genetic variation on drug response in patients by correlation gene expression with drug toxicity
63
What does Genomics England aim to do?
Sequence 100,00 patients with cancers and rare disorders to produce new capability in genomic medicine for NHS

IMS (53 decks)

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