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Genetics > General > Flashcards

General Flashcards

1
Q

What does virulence mean?

A

The ability of a pathogen to cause disease. Its severity.

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2
Q

What Sugar is present in DNA nucleotides?

A

Deoxyribose sugar - is a pentose sugar.

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3
Q

Which carbon of the pentose sugar are nitrogenous bases attached to in a nucleotide?

A

1’

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4
Q

What carbon of the pentose sugar are phosphate groups attached to in a nucleotide?

A

5’

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5
Q

Which other nitrogenous base is bonded to Adenine and how many hydrogen bonds are present ?

A

Thymine

2

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6
Q

Which other nitrogenous base is bonded to Cytosine and how many hydrogen bonds are present ?

A

Guanine

3

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7
Q

How is DNA anti-parallel and what process is this helpful in?

A

One strand runs 3’ to 5’. The other runs 5’ to 3’.

Semi-conservative replication of DNA.

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8
Q

What are the 2 groove types in DNA?

A

Minor groove major groove.

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9
Q

How are the grooves within DNA helpful?

A

They allow stains such as SYBR green and Ethidium Bromide to fit into the grooves and stain DNA molecules. Useful in PCR and gel electrophoresis.

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10
Q

Name a dyes used in PCR/ gel electrophoresis.

A

SYBR green

Ethidium Bromide

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11
Q

What are enhancers in a DNA sequence? And what type of organisms are they most used in?

A

Enhancers are sequences that are linked with a promoter region and enhance the activity of the promoter region due to their associates with protein transcription factors. Enhancers mediate most selective gene expression in eukaryotes.

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12
Q

Which nitrogenous bases are purine?

A

Guanine and Adenine

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13
Q

Which nitrogenous bases are pyrimidine ?

A

Thymine and Cytosine

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14
Q

How many rings in a purine base?

A

2

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15
Q

How many rings in a pyrimidine base?

A

1

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16
Q

What is an intron?

A

A non-coding sequence of nucleotides which don’t code for an amino acid sequence or polypeptide chain.

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17
Q

What is an exon?

A

A coding region of nucleotides which code for a specific amino acid sequence.

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18
Q

When are introns present in mRNA?

A

Present in Pre-mRNA but not in mRNA.

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19
Q

How are introns removed from DNA?

A

Splices out by spliceosome enzyme.

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20
Q

What are intergenic regions of DNA and how are they useful?

A

They are non-coding sequences of DNA located between genes. These DNA sections are methylates to help maintain genomic integrity and prevent mutations.

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21
Q

What is illegitimate recombination?

A

2 unrelated DNA sections are joined.

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22
Q

Why are repetitive elements of DNA methylated?

A

To prevent neighbouring genes being transcribed when they are not supposed to by the presence of strong promoter regions. Helps maintain genomic integrity and prevent mutations. Prevents illegitimate recombination.

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23
Q

What are Pseudogones?

A

Former genes that have accumulated mutations that make them non-functional.

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24
Q

What is another name for Pseudogenes?

A

Vestigial genes

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25
Q

How are Pseudogenes often formed? (3 ways)

A

A gene whose protein is needed for survival.
When a gene is duplicated
Processed pseudogene.

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26
Q

What is a processed pseudogene?

A

Result of a DNA copy of mRNA being inserted into genome.

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27
Q

How is a pseudogene created when a gene is duplicated?

A

When a gene is duplicated one becomes a Pseudogenic gene and is non-functional and mutated. This doesn’t harm the organism because the other version of the gene remains functional and non-mutates.

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28
Q

Describe how DNA is packed to become a metaphase chromosome.

A

DNA helix wraps around histones to form nucleosomes (beads on a string). Loops of thick chromatin fibres from and are then further compacted into looped domains. The compact metaphase is then formed.

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29
Q

What makes the DNA pacing process highly specific?

A

Specific genes are always in the same place in the packed metaphase chromosome.

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30
Q

Why is heterochromatin hard to translate?

A

It is very densely and tightly packed so not many proteins are able to enter.

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31
Q

Why doesn’t heterochromatin contain much DNA?

A

Has long stretches of Satellite DNA.

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32
Q

Is euchromatin easy or hard to translate/transcribed and why?

A

Easy to transcribe because DNA is loosely packed around histones.

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33
Q

What is a solenoid?

A

6 nucleosomes joined together.

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34
Q

What is the area on a Solenoid where a lot of Adenine and Thymine are present?

A

Scaffold Attachment Area (SAR).

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35
Q

What is the scaffold attachment area on solenoids?

A

This is the sections of DNA where alot of Adenine and Thymine are present.

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36
Q

How is a super solenoid formed?

A

When SAR regions of multiple solenoids attach.

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37
Q

Who presented the structure of the DNA helix and in what year?

A

James Watson and Francis Crick.

1953

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38
Q

What method did Watson and Crick use to decide the structure of DNA?

A

Stick and ball methods.

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39
Q

What method did Maurice Wilkins use to decide the structure of DNA?

A

X-ray diffraction.

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40
Q

How does X-ray diffraction work when deciding the structure of DNA? (Brief).

A

X-rays shine onto and then bounce off the DNA molecule and create a complex pattern on photographic film. The film indicates the structure of DNA.

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41
Q

What allowed Watson to deduce that the sugar-phosphate backbone of DNA is smooth?

A

The bonding between A&T and G&C are exactly the same length. Therefore each rung of the DNA helix will be equal in length.

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42
Q

A famous experiment demonstrated that DNA could direct viral replication, providing evidence that DNA is the genetic material. Which scientists were directly involved in this experiment?

A

Alfred Hershey and Martha Chase

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43
Q

What is the purpose of Topoisomerases during DNA replication?

A

Work ahead of the replication fork to prevent supercoiling as the DNA opens.

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44
Q

What is Chargaffs ratio?

A

In a DNA sequence the ratio of A:T = C:G

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45
Q

Why is it impossible to have triple stranded DNA?

A

Some of the van Der Waals forces in DNA are too small/ weak to allow this.

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46
Q

Why can’t DNA have ribose sugar ? Why must it be de-oxyribose?

A

The extra oxygen atom would make the van Der Waals intermolecular forces become too close together and would change the physical structure of DNA.

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47
Q

When do neutrophils form?

A

During the initial stages of infection.

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48
Q

What cell type do Macrophages arise from?

A

Monocytes.

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49
Q

What are C3P and what is their purpose in immunity?

A

Recognise pathogens, attach to the surface of the pathogen and trigger an immune response. Compliment system with macrophages.

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50
Q

How is an MHC molecule formed?

A

Dendritic cells engulf the pathogenic antigens and present them on their surface to create a MHC molecule.

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51
Q

What happens when a MHC molecule has formed in the immune system ?

A

Cytotoxic T cells are activated and cause infected human cells to undergo autolysis and therefore kill the pathogen.

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52
Q

What are the 3 steps of DNA replication?

A

Initiation, Elongation, Termination.

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53
Q

Where does copying of DNA occur?

A

Replication fork

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54
Q

What is the purpose of DNA helicase in DNA replication?

A

Spins to unravel DNA helix whilst breaking hydrogen bonds between complimentary base pairs.

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55
Q

What is the leading strand of DNA?

A

The 3’ strand.

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56
Q

What is the lagging strand of DNA?

A

5’ strand - replicated with Okazaki fragments.

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57
Q

What direction does DNA helices work in?

A

5’ to 3’

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58
Q

When does DNA replication occur in Eukaryotes?

A

The S phase.

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59
Q

How was E.coli used to determine the semi-conservative nature of replicated DNA ?

A

Density gradient centrifugation was used. Before replication, only heavy nitrogen was present in the DNA. After 1 replication, there was an intermediate of both heavy and light nitrogen present. Couldn’t be conservative replication because no mixture of weighted nitrogen would be present. After the second replication , 75% of light nitrogen and 25% of heavy nitrogen was present - couldn’t be dispersive replication.

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60
Q

Describe the DNA that will be present after 1 and 2 replications in semi-conservative replication.

A

After 1 replication - 2 copies of DNA, both with one parent strand and one daughter stand.
After 2 replications - 2 copies with both parents strands, 2 copies with one parents and one daughter strand.

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61
Q

Name the overall features of DNA replication.

A 
Semi conservative.
Starts at the origin.
Synthesis in the 5' to 3' direction.
Unidirectional or bidirectional. 
Semi-discontinuous. 
RNA primers required.
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62
Q

Where does DNA replication start?

A

The origins

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63
Q

How many origin points for DNA replication do Eukaryotes have?

A

Many

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64
Q

What is the benefits of Eukaryotes having many origin points for DNA replication to begin?

A

Prevents replication stalling which can be harmful to a cell. Ensures that replication can happen rapidly. Acts as a backup incase some enzymes are unable to complete replication of one section of DNA.

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65
Q

Why can DNA synthesis only occur in the 5’ to 3’ direction?

A

DNA helices only works 5’ to 3’.

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66
Q

How does bidrectionality occur during DNA replication?

A

Replication forks move in opposite directions.

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67
Q

What are the benefits of bi-directional DNA replication?

A

Allows more than one section of DNA to be replicated at one time ad prevents replication stalling.

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68
Q

What is the REPLICON in DNA replication?

A

The region of DNA that is replicated from the start of the replication fork.

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69
Q

Are all origins of DNA Replication always active?

A

No - Only about 15% of origins are active at one time.

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70
Q

What is the benefit of only having some origins active at one time during DNA replication?

A

This allows time for proof reading and prevents mistakes in DNA replication.

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71
Q

What makes DNA replication semi-discontinuous ?

A

DNA polymerase works 5’ to 3’ so only the leading strand can be replicated continuously. The lagging strand is replicated discontinuously via Okazaki fragments.

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72
Q

Outline the process of DNA replication initiation.

A
  1. Pre-replication complex binds to origin.
  2. Accessor proteins bind to PRC.
  3. Components of the PRC are activated by Phosphorylation
  4. DNA polymerase are recruited
  5. Replication is initiated in the S phase
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73
Q

Why are accessory enzymes required in DNA replication initiation?

A

Allows enzymes such as DNA helicase and DNA polymerase to be able to bind to the parent strand.

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74
Q

What is the purpose of DNA gyrase in DNA replication?

A

Makes single strand nicks to relax supercooling. (Creates a cut in the double strand of DNA to help unwind the DNA and prevent the stress of un-winding), seals gaps in the sugar-phosphate backbone.

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75
Q

What is the purpose of RNA primase in DNA replication?

A

Catalyses he production of RNA primers?

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76
Q

What is the other name for RNA primase?

A

DNA polymerase alpha

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77
Q

What is the purpose of DNA polymerase during DNA replication?

A

Adds nucleotides in the 3’ to 5’ direction

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78
Q

What direction does DNA polymerase act in ?

A

5’ to 3’

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79
Q

What is the process of DNA replication in the leading strand?

A

Topoisomerases unwind the DNA helix and disrupt the sugar-phosphate backbones. DNA helices works 5’ to 3’ to break the hydrogen bonds between complimentary nucleotides. DNA primase adds RNA primers to the DNA. DNA polymerase adds complimentary nucleotides in the 3’ direction.

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80
Q

What are RNA primers produced by ?

A

Polymerase alpha

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81
Q

What is the purpose of DNA primase in DNA replication?

A

Adds RNA primers to the DNA.

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82
Q

Describe the process of DNA replication of the lagging strand.

A

Topoisomerase unwinds the DNA helix and disturbs the sugar-phosphate backbones. DNA helices breaks hydrogen bonds between complimentary base pairs. DNA primase adds many RNA primers to the lagging strand. DNA polymerase is then able too add nucleotides in the 3’ direction at each primer site. This creates Okaaki fragments. Polymerase delta uses RNA primers as an anchor to add bases to the lagging stand. RNAse H degrade RNA primers so that only DNA is left. A series of DNA with a gap in their backbone has been replicated. DNA ligase joins sugar-phosphate backbones.

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83
Q

What is the purpose of RNAse H in DNA replication?

A

Degrades RNA primers so that only DNA is present in the final replicated DNA.

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84
Q

What is the purpose of DNA ligase in DNA replication?

A

Join the sugar-phosphate backbones in the lagging strand.

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85
Q

What triggers the termination phase of DNA replication?

A

The collision of two replicative forks between two active replication origins.

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86
Q

What are the reasons why DNA replication may enter the termination phase?

A

Chromosome ends, replication issues, can’t fit another primer, lose chromosomal DNA.

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87
Q

What is the purpose of the telomere?

A

Protective cap at the end of the DNA strand. Prevents chromosome fusion by non-homologous ends joining.

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88
Q

What molecules is Telomerase made of ?

A

hTERT - human telomerase reverse transcriptase.

hTP - telomerase RNA

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89
Q

What type of template (DNA or RNA) does telomerase use?

A

RNA

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90
Q

What is the purpose of the telomerase enzyme in DNA replication?

A

Extends the telomere - adds repeating sequences of nucleotides to the 3’ end of the DNA strand.

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91
Q

What happens when the telomere shrinks and becomes very small?

A

Cellular senescence

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92
Q

What is cellular Senescence ?

A

Once the telomere shrinks to a certain extent, the cell stops dividing as he telomere is lost. Cell morphology changes and gene mutations may occur.

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93
Q

What are cell morphology changes?

A

Breakdown of the cell wall, disfunction of organelles, cells become unattached from each other etc.

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94
Q

Which strand in mitochondrial DNA is used for replication?

A

The H strand in mammalian mitochondrial DNA.

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95
Q

What happens to the original L strand of mitochondrial DNA during mitochondria DNA replication?

A

Remains single stranded and un-replicated.

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96
Q

Which side of a DNA strand add nucleotides to ?

A

3’ end

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97
Q

Where is DNA polymerase Gamma present and what is its purpose?

A

In the mitochondria . Used to Replicate mitochondrial DNA .

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98
Q

Where are all DNA Polymerases (except DNA polymerase gamma) located?

A

Nucleus

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99
Q

Where is DNA polymerase beta present and what is its function?

A

Nucleus of non-dividing cells. Helps aid DNA repair .

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100
Q

Where do DNA polymerases add new nucleotides to on the strand ?

A

3’ end hydroxyl group .

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101
Q

How does DNA polymerase I act as a exonuclease in DNA replication?

A

Removed ribonucleotides in the from the 5’ end of Okazaki fragments allowing them to be replaced with deoxyribonucletoides so that fragments consist of DNA only .

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102
Q

What shape is an E.Coli chromosome?

A

Circular

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103
Q

How is telomerase able to be complimentary and act on the telomere?

A

It carries its own template RNA which is complimentary to the telomere repeat sequences .

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104
Q

What happens to the overhanging 3’ end of the chromosomes in eukaryotes at the end of DNA replication?

A

They form loops .

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105
Q

Which strand of DNA is the coding strand?

A

The lagging strand

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106
Q

Which strand of DNA is the non-coding strand?

A

The leading strand

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107
Q

How many types of RNA polymerase exist in eukaryotes?

A

3

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108
Q

How many types of RNA polymerase exist in bacteria?

A

1

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109
Q

What is the purpose of enhancer sequences in DNA replication and how do they work?

A

Bind to activator proteins and alter the 3D structure of DNA to help attract DNA Polymerase II and therefore regulate transcription .

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110
Q

What proteins facilitate looping of the DNA during DNA replication and which proteins does looping allow to interact?

A

Activator proteins - Allow proteins bound to the enhancer and proteins bounds to the promoter to interact .

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111
Q

What proteins prevent the looping of DNA?

A

Repressor proteins .

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112
Q

Are terminator genes located upstream or downstream from the coding region?

A

Downstream

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113
Q

Write an overall definition for eukaryotic transcription.

A

The use of DNA as a template to produce mRNA.

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114
Q

Why is DNA changed into mRNA before entering the cytoplasm?

A

The cytoplasm would be too hostile and degrade the DNA.

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115
Q

Where does eukaryotic transcription occur?

A

The nucleus

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116
Q

What is the difference I the sugar present in DNA and RNA?

A

RNA has Ribose but DNA has 2’- Deoxyribose.

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117
Q

What is the different base in RNA compared with DNA?

A

Thymine in DNA, Uracil in RNA.

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118
Q

What is the structural different between uracil and thymine?

A

Uracil has one less methyl group than Thymine.

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119
Q

What is the advantage of Thymine having the extra methyl group compared to Uracil?

A

The methylation makes the DNA more protected and restricts Thymine to only binding with Adenine.

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120
Q

What is the general function of mRNA?

A

Codes for proteins

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121
Q

What is the general function of rRNA?

A

Form the basic structure of the ribosome and catalyse protein synthesis.

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122
Q

What is the general function of tRNA?

A

Used in protein synthesis as an adaptor between mRNA and amino acids.

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123
Q

What are the benefits of having mRNA as an intermediate between RNA and DNA?

A

Controls the location and transcription of DNA. Allows amplification. mRNA is less likely to be degraded in the cytoplasm than DNA.

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124
Q

How does having mRNA as an intermediate allow amplification of transcription?

A

In DNA we only have one copy of a gene so transcription would be very slow. Whereas using mRNA means many copies of the gene can be present and therefore allow alot of transcription of the gene to occur at once.

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125
Q

What is required for RNA polymerase to bind to DNA?

A

Transcription factors.

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126
Q

What are transcription factors?

A

Proteins that bind in or near the promoter regions of the gene or at regulatory gene sequences to control gene expression.

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127
Q

What are the optional sequence elements that transcriptional factors bind to?

A

Basal promoter elements - in or near promoter regions.

Proximal promoter elements - sequences that are further away from the promoter region.

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128
Q

What are cis-acting transcriptional factor elements?

A

Sequence elements present on the same DNA molecules as he gene they affect.

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129
Q

What are trans-acting transcriptional factors?

A

Sequence elements that interact with genes on any DNA molecule or gene within the cell. They are able to move throughout the cell.

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130
Q

Where is RNA Polymerase I found and what is it overall purpose?

A

Nucleolus

Transcribes rRNA

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131
Q

Where is RNA Polymerase II found and what is its overall purpose?

A

Nucleus

Transcribes mRNA and genes for some species of small RNA.

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132
Q

Where is RNA III found and what is its overall purpose?

A

Transcribes tRNA and 5S rRNA genes.

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133
Q

Describe the complex of RNA polymerase II.

A

It is a hollow enzyme complex made up of many different accessory proteins such as RNA Polymerase II enzyme, a subset of general transcription factors and many regulatory proteins.

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134
Q

What is the transcription initiation complex and what is its purpose?

A

TATA box is surrounded by a selection of different transcription factors.
Allows the un-zipping of DNA for replication to occur.

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135
Q

Describe the elongation process of DNA transcription.

A

The dimer protein ‘FACT’ binds to nucleosomes immediately ahead of the transcribing RNA polymerase II. This partly dissembles the nucleosome (removes 2 of the 8 histones) so that RNA Polymerase II can transcribe the DNA wrapped around the nucleosome. ‘FACT’ the reassembles the nucleosome being RNA Polymerase II by returning the missing histones.

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136
Q

Exactly how does the dimer protein ‘FACT’ disrupt the nucleosome during DNA transcription?

A

Removes 2 of the 8 histones.

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137
Q

What are the 3 stages of DNA transcription?

A

Transcription initiation complex, elongation, termination.

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138
Q

Describe the allosteric model of DNA transcription termination.

A

At a termination polyadenylation signal, the binding of the RNA Polymerase II and its accessory proteins is disabled. Polymerase II can no longer bind to the DNA and transcribe it.

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139
Q

What are the 2 models for DNA transcription termination?

A

Allosteric model and Torpedo model.

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140
Q

Describe the torpedo model for the termination of DNA transcription.

A

RNA polymerase II produces mRNA to be longer than the gene. mRNA is cut and detached from RNA Polymerase II at the cleavage site.
Xrn2 can bind to the end of the remaining mRNA which is still attached to RNA polymerase II and degrade the remaining DNA towards the enzyme. When Xrn2 collides with RNA Polymerase II, RNA polymerase is knocked off the DNA strand terminated transcription.

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141
Q

How is Pre-mRNA processed to form mRNA ?

A

A cap is added to the 5’ and a Poly A tail is added to the 3’.
Splicing introns using a spliceomere.

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142
Q

What is capping of Pre-mRNA during transcription and what is the purpose of this?

A

Addition of a cap to the 5’ end of Pre-mRNA by the capping enzyme prevents degradation of the RNA and is also needed for recognition of the binding ribosomes.

143
Q

What enzyme does the capping of Pre-mRNA require during transcription ?

A

Guanylytransferase.

144
Q

What is the purpose of the PolyATail being added to the Pre-mRNa during DNA transcription.

A

Acts as a protector and prevent degradation of the RNA.

It is also used to determine the length of the mRNA.

145
Q

How are introns recognised for splicing?

A

Introns are recognised by consensus sequences at the 5’ and the 3’ splice junctions.

146
Q

Why must introns be removed from the Pre-mRNA - what is the need for this?

A

Splicing must occur to allow the mRNA to be exported from nucleus to the cytoplasm for translation.

147
Q

What enzyme is splicing carried out by?

A

Spliceosome.

148
Q

What is alternative splicing?

A

Alternative splicing is the production of multiple different proteins from one gene sequence based on the specific order and number of axons which are combined after axons are removed.

149
Q

What is Tissue-specific splicing?

A

Splicing of the gene is different in different genes to control cell functioning. The exons that have been spliced into the sequence may be different or in different positions.

150
Q

What molecules make up the spliceosomes?

A

A complex of proteins and snurps.

151
Q

What does snurps Stand for?

A

Small nuclear ribonuclear particles.

152
Q

What transcriptional control sequence elements control gene expression?

A

Enhancers, silencers, terminators, insulators.

153
Q

What do enhancer sequences do in transcription ?

A

Stimulate transcription of a gene whose function is not critically dependent on their precise position or orientation.

154
Q

What do silencer sequences do in transcription ?

A

Promote the formation of condensed chromatin structures in a localised region. These structures block access for enzymes needed for gene transcription. Gene transcriptions stops.

155
Q

What are terminator sequences in gene transcription?

A

Cause RNA polymerase II to terminate transcription.

156
Q

What are insulator sequences in gene transcription ?

A

Block or insulate the spreading of transcription enhancers and transcription silencers.

157
Q

Name some transcriptional factors.

A

Activators, repressors, Coactivators, Basal transcription factors.

158
Q

What are activator transcription factors?

A

Proteins that bind to genes at enhancer sequences and speed up translation.

159
Q

What are repressor transcription factors?

A

Proteins that bind to selected sets of genes at silencer sites and slow transcription.

160
Q

What are Coactivator transcription factors>

A

Intergrate signals from activator and repressor transcription factors.

161
Q

What are basal transcription factors?

A

In response to injunctions from activators, these factors position RNA polymerase at the start of the gene and initiate the transcription process.

162
Q

What is methylation of DNA and how does it affect translation?

A

Adding methyl groups to the DNA makes it wrap more tightly around the histone. Gene expression is repressed.

163
Q

What is DNA acetylation and how does it affect translation?

A

Adding acetyl groups causes DNA to become less tightly wrapped around the histones to create a Euchromatin complex. More gene expression and translation can occur.

164
Q

What enzymes is DNA acetylation controlled by?

A

HAT enzymes.

165
Q

What are CPG islands in DNA and what is their purpose in transcription?

A

Areas with alot more cytosine and guanine than average. Help control DNA methylation as cytosine is prone to being methylated. Therefore makes CGP area more tightly packed around histones and gene expression in this region is repressed or stopped.

166
Q

Can environmental effectors affect DNA methylation ?

A

Yes - for example diet.

167
Q

How many types of RNA polymerase do bacteria have?

A

1

168
Q

How many types of different RNA Polymerase do Eukaryotes have?

A

3

169
Q

How do enhancer regions regulate gene expression?

A

They bind with activator proteins and change the 3D structure of DNA to help attract RNA polymerase II, therefore regulating transcription.

170
Q

What is meant when transcription factors are often described as strong or weak ?

A

Describes their effect on the rate of transcription.

171
Q

What happens if the strength of transcription factors is altered?

A

It can cause disease.

172
Q

How are enhancer sequences Brought closer to the gene they need to affect?

A

By the looping of DNA.

173
Q

What is present at the end of transcription?

A

A mature mRNA strand.

174
Q

What acts as a template for the translation process?

A

Mature mRNA strand.

175
Q

How is the genetic code universal?

A

The same bases codons code for the same amino acids in all life forms.

176
Q

What are 2 main features of the genetic code?

A

Universal and degenrate

177
Q

What is meant by a genetic code being degenerate?

A

Some amino acids can be coded for by more than one codon.

178
Q

What is the initiator codon?

A

AUG

179
Q

What does amino acid AUG code for ?

A

Methionine

180
Q

What are the 3 possible stop codons?

A

UAA, UAG, UGA

181
Q

What are non-essential amino acids?

A

Can be created by the body from essential amino acids.

182
Q

What are essential amino acids>

A

Cannot be created by the body and must be consumed.

183
Q

What are reading frames and in what form of genetic information are they present?

A

DNA and RNA. The way in which the geek sequence is read depends on the specific base and codon we start at. This decides the reading frame.

184
Q

What is an open reading frame>

A

The only sections of genetic information that will produce a functioning protein and have the ability to be translated. They always contain a start and stop codon.

185
Q

Describe the general shape of a tRNA molecules.

A

Cliover

186
Q

In what way is tRNA complimentary to mRNA.

A

The anticodon on tRNA is complimentary to a codon on mRNA.

187
Q

How is an amino acid attached to tRNA ?

A

Covalently bonded to the attachment site of tRNA.

188
Q

Is the process of translation passive or active?

A

Active - requires ATP.

189
Q

What enzyme is used for the charging process in translation?

A

Aminoacyl tRNA synthesise.

190
Q

What is the process of changing in translation?

A

The covalent bonding of an amino acid to a tRNA molecule using ATP. Active process.

191
Q

Outline the process of charging in translation.

A

tRNA synthesise binds to ATP and a specific amino acid. Amino acid - AMP complex is formed and a specific tRNA molecule is recruited. The tRNA is bound to the amino acid and the AMP is released. Charged tRNA is produced.

192
Q

What does AMP stand for>

A

Adenosine monophosphate.

193
Q

How many binding sites do ribosomes used in translation have and what are these sites called?

A

3
P - Peptidyl tRNA binding sie
A - Aminoacyl tRNA binding sie
E - Exit site

194
Q

Outline the initiation process of translation.

A

Complex of the small ribosomal subunit and initiator tRNA bind to the 5’ cap.
The complex scans to find the start codon which is complimentary to its anticodon.
Initiator tRNA binds to the start codon and stalls the transition process. This allows the large ribosomal subunit to bind to the mRNA.
Initiator complex is held within the P site of the ribosome.

195
Q

Outline the elongation process of translation.

A

The second tRNA with an anticodon complimentary to the mRNA codon stays in the adjacent A site.
Peptide bonds form between the two adjacent amino acids.
The amino acid from the first tRNA molecule is transferred to the second tRNA molecule.
The first tRNA enters the E site and is therefore removed. The second tRNA moves to the P site. A new tRNA molecule moves into the A site and the process continues.

196
Q

Outline the termination process of translation.

A

Release factor is complimentary and binds to the stop codon. This prevents the ribosome from moving past the release factor and prevents further translation.
The polypeptide chain, ribosomes and release factors are then released.

197
Q

What happens to the ribosomes after translation?

A

They are recycled.

198
Q

What type of bonds are between amino acids?

A

Peptide.

199
Q

What is the product of translation?

A

Primary protein - specific sequence of amino acids.

200
Q

Describe the tertiary structure of proteins.

A

The folding of the chain into a 3D globular shape due to ionic bonding, hydrophobic interactions, hydrogen bonding and disulphide bridges between the side chains of different amino acids.

201
Q

Describe the quaternary structure of amino acids.

A

The presence of more than one polypeptide chain or the presence of prosthetic groups.

202
Q

What is the prosthetic group in haemoglobin structure?

A

Fe 2+ (iron).

203
Q

What is protein heterogeneity?

A

The use of identical proteins in different cells doing different jobs.

204
Q

What is trimming as a form of post-translational modification?

A

Removal of a specific part of the translated protein.

205
Q

What is the purpose of trimming in post-translational modification?

A

It allows some enzymes to move from their inactive form to their active form.

206
Q

What are the 3 pathways for degradation of mRNA?

A

Deadenylation dependent mRNA decay.
Deadenylation independent mRNA decay.
Endonulease-mediated mRNA decay.

207
Q

Describe deadenylation dependent mRNA decay.

A

Removing the Poly-A-Tail from the 3’ end of mRNA and the cap from the 5’ end of mRNA so that it is open to degradation by exonucleases at both ends.

208
Q

What is deadnylation independent mRNA decay?

A

Removal of the cap from the 5’ end of mRNA so that it is open to degradation at the 5’ end.

209
Q

Describe endonuclease-mediated mRNA decay.

A

mRNA is cut by endonuclease meaning it now has un-protected end sites which can be degraded by exonucleases.

210
Q

What is the process of protein degradation in translation?

A

Ubiquitination

211
Q

Outline the process of protein degradation by ubiquitination.

A

Targets proteins to the proteosomes which break the down into smaller peptide molecules to be recycled and used for other purposes.

212
Q

Which strand of mRNA is transcribed?

A

Neither - both mRNA can be transcribed.

213
Q

Where are terminator genes in relation to the coding region of DNA?

A

Downstream

214
Q

Where does translation happen?

A

Inside ribosomes

215
Q

What are ribosomes made of?

A

Protein and RNA

216
Q

What allows some tRNA molecules to bind to multiple codons?

A

Wobble coding

217
Q

What is wobble coding in terms of translation?

A

Base pairing rules are altered meaning a G in the anticodon can pair with a C or a U in a codon.

218
Q

What are the benefits of wobble coding in terms of translation?

A

Fewer tRNA molecules are needed to cover the whole genetic code whilst still making sure that the code is read accurately.

219
Q

What are the purpose of aminoacyl-tRNA synthetases?

A

There are different synthetases for each amino acid. Each synthate will only recognise its amino acid and tRNAs. Both the tRNA and the amino acid bind to the enzyme. The enzyme then links the tRNA to the amino acid using energy from ATP.

220
Q

How do Aminoacyl-tRNA synthetases avoid mistakes?

A

They have proofreading machinery.

221
Q

Which way are the mRNA codons read to allow translation?

A

5’ to 3’

222
Q

What proteins recognise stop codons?

A

Releasing factors

223
Q

How do releasing factors stop translation?

A

They prevent peptide bonds forming to new amino acids by adding a water molecule to the last amino acid of the chain. This therefore separates the tRNA molecule and releases the newly made polypeptide chain.

224
Q

What is the main difference between Prokaryotic and Eukaryotic DNA replication?

A

Prokaryotes use operons.

225
Q

Where does transcription/ translation occur in Eukaryotes ?

A

Transcription in the nucleus and translation in the cytoplasm.

226
Q

What enables transcription and translation in Eukaryotes to occur in two different places?

A

The membrane boundary

227
Q

Where does transcription and translation occur in prokaryotes?

A

Both in the nucleus

228
Q

Why do both transcription and translation occur in the nucleus in prokaryotes and what effect does this have?

A

There are no membrane boundaries so the processes can’t be separated. This means that translation and transcription will occur at the same time.

229
Q

What is it called when transcription begins when translation is still occurring and what cell type does this occur in?

A

Concurrent DNA synthesis.

Prokaryotes because there is no membrane boundaries to separate transcription and translation.

230
Q

How many sections are there to prokaryotic genes?

A

3

231
Q

What are the 3 sections of prokaryotic genes?

A

Promoter region (5’), RNA coding sequence, Terminator region (3’).

232
Q

Why does supercoiling occur in bacterial/ prokaryotic DNA?

A

The DNA is too large to fit into the bacterial cell but does not have histones to undergo the usual DNA packaging so must be supercoiled.

233
Q

Outline the process of supercoiling in bacterial DNA.

A

The circular DNA of bacteria forms looped domains by using accessory proteins. Each looped domain is then coiled. This forms condensed DNA which is small enough to fit into the prokaryotic cell.

234
Q

What are the 2 types of supercoiling? Explain both.

A

Positive - Twisting in the same direction as the double helix.
Negative - Twisting in the opposite direction to the double helix.

235
Q

How many origins of replication are there on DNA and why?

A

One origin because bacterial DNA is smaller than eukaryotic DNA.

236
Q

What DNA Polymerases are used for Prokaryotic DNA replication?

A

DNA polymerase 3

DNA polymerase 1

237
Q

What is the. purpose of DNA polymerase 3 in prokaryotic DNA replication?

A

Used to replicate the leading strand.

238
Q

What is the purpose of DNA polymerase 1 in prokaryotic DNA replication?

A

Used to replicate the lagging strand by forming Okazaki fragments.

239
Q

Which topoisomerase is used in Prokaryotic DNA replication and what is it used for?

A

Topoisomerase 4 - used to detach the two double-stranded, circular DNA samples to produce 2 identical circular DNA samples.

240
Q

Are Prokaryotic genes usually on or off and what does this mean for termination?

A

They are usually turned on which means repressor proteins and required to stop transcription.

241
Q

What type of enzyme is RNA polymerase in Prokaryotic DNA replication ?

A

Holoenzyme

242
Q

What is the make-up of a holoenzyme?

A

5 subunits and a sigma factor

243
Q

What are the benefits of having a RNA polymerase holoenzyme in Prokaryotic DNA replication?

A

The holoenzyme can bind directly to the DNA strand and therefore doesn’t require the accessory proteins that eukaryotes do for DNA replication.

244
Q

What is the purpose of the sigma factors in the RNA Polymerase holoenzyme used in Prokaryotic DNA replication?

A

Sigma factors bind to -35 and -10 sequences in the DNA to anchor the RNA polymerase to the DNA and initiate transcription. This also cases the DNA to have an open complex with a DNA transcription bubble.

245
Q

What happens to the sigma factor on the RNA polymerase holoenzyme complex when prokaryotic DNA replication is completed?

A

The sigma factor is released and the RNA transcription bubble continues down the strand. The sigma factor is either recycled or recruited for another process.

246
Q

What are the 2 types of Prokaryotic transcription termination?

A

Rho-independent

Rho-dependent

247
Q

Outline the process of Rho-independent prokaryotic transcription termination.

A

There is a signal region (A section of DNA that is repeated as an inverse in the sequence again and then followed by a short string of adenines). This causes the RNA polymerase to weaken its connection with the RNA sequence and dissociate from the sequence. Transcription stops.

248
Q

Outline the process of Rho-dependent transcription termination in prokaryotes.

A

The Rho factor binds to the end of the RNA chain and slides towards the transcription bubble. It then collides with the RNA polymerase and causes it to fall of the RNA strand. Transcription can no longer occur.

249
Q

What are the purpose of the -35 and -10 sections of prokaryotic genes ?

A

They allow specific regions of the RNA polymerase holoenzyme to bind.

250
Q

What size are prokaryotic ribosomes and what subunits are they made up of?

A

70s - 50s subunit and a 30s subunit

251
Q

What size are eukaryotic ribosomes and what subunits are they made. up of?

A

80s - 60s subunit and 40s subunit

252
Q

Outline the process of initiation of translation in prokaryotes. (How the ribosome binds to the prokaryotic DNA).

A

16s rRNA binds to mRNA at the Shine-Dalgarno sequence.
Initiation factor 3, the 30s ribosomal subunit and the shine-dalgarno sequence interact.
Initiation factor 2 promotes the binding of the first tRNA molecule.
The 50s ribosomal subunit then associates to the complex and IF2 and IF3 are released.

253
Q

How many ribosomes translate prokaryotic mRNA at one time?

A

Many

254
Q

How does the process of translational elongation differ in prokaryotes and eukaryotes?

A

They are exactly the same.

255
Q

How many release factors do bacteria have?

A

3

256
Q

How many release factors do Eukaryotes have?

A

1

257
Q

What are the purpose of release factors in prokaryotic DNA replication?

A

Facilitate the release of ribosomal subunits from the RNA chain.

258
Q

What is the main method of gene expression in prokaryotic DNA replication?

A

Operons

259
Q

What are operons ?

A

Operons are related genes controlled by the same promoter region.

260
Q

What is the main overall advantage of operons?

A

They rapidly turn on and off gene expression which saves energy because proteins which are not needed are no longer produced.

261
Q

How do operator regions used to switch off operon genes?

A

Operon genes are usually the binding site for a specific repressor protein. The repressor protein binds and acts as a physical block to present transcription.

262
Q

How do activator regions of operons increase the rate of prokaryotic DNA replication?

A

Activator regions allow the binding of other proteins to increase the rate of transcription and therefore produce alot more mRNA.
Many regulatory activator and repressor proteins can also be switched on or off by small molecules within the cell.

263
Q

What is the general purpose of the lac operon?

A

The lac operon is used to switch off lactose catabolism when there is little energy (glucose available). The cell can then use the lac operon as an energy source.

264
Q

What is the general purpose of the lac operon?

A

The lac operon is used to switch off lactose catabolism when there is little energy (glucose available). The cell can then use the lac operon as an energy source.

265
Q

How does the lac operon work when there is very little lactose in the cell and how is this beneficial?

A

Repressor genes are bound tightly to the operon meaning that gene expression becomes so little that it is negligible.
The cell therefore saves energy by lowering transcription and translation of enzymes that are not required.

266
Q

How does the lac operon work when there is very little lactose in the cell and how is this beneficial?

A

Repressor genes are bound tightly to the operon meaning that gene expression becomes so little that it is negligible.
The cell therefore saves energy by lowering transcription and translation of enzymes that are not required.

267
Q

Does absence of glucose in the cell activate or inactive the lac operon?

A

Activates it.

Enzymes needed for lactose catabolism are produced.

268
Q

How does allolactose affect the lac operon?

A

Allolcatose binds to the repressor proteins and stops it from binding to the operator. This means that RNA polymerase can be used to transcribe the genes and lactose can be metabolised.

269
Q

What happens with the lac operon when no lactose or glucose are present?

A

There is no transcription.
cAMP levels are high because glucose levels are low. So CAP is active and will be bound t the DNA. Lac repressor will be bound to the operator due to the absence of allolactose. This acts as a roadblock to RNA polymerase and prevents transcription.

270
Q

What type of operons are used to switch other operons off?

A

Corepressor / Trp operon

271
Q

What type of operons are used to switch other operons off?

A

Corepressor / Trp operon

272
Q

How does the tryptophan operon work when there is high tryptophan?

A

No transcription occurs because no more tryptophan is needed.
Tryptophan binds repressor proteins which is then used to prevent RNA polymerase binding to the promoter region by acting as a mechanical block. No mRNA is therefore produced.

273
Q

What is attenuation of tryptophan and how does this process work when there is high tryptophan levels?

A

A stem loop transcriptional terminal is present and causes a hairpin loop. One of the domains of the stem loop is covered so the two domains can’t interact. This is inhibitory to tryptophan transcription because it stops binding of the ribosome and also causes dissociation of RNA polymerase.

274
Q

What happens to the tryptophan operon when there is low tryptophan levels?

A

Transcription must occur.

RNA polymerase can bind to the promoter region and the genes can be transcribed.

275
Q

What is attenuation of the tryptophan operon when there is low tryptophan levels?

A

Both domains of the hairpin loop are able to interact and transcription of tryptophan is promoted.

276
Q

What is the main difference between how DNA polymerase and RNA polymerase work?

A

RNA polymerase doesn’t require a primer to initiate RNA synthesis but DNA polymerase does.

277
Q

What is the overall purpose of the sigma section of the RNA polymerase holoenzyme?

A

Find the correct promoter regions for translational initiation which must start at the beginning of a gene for the RNA to be functional.

278
Q

Why do gene sections such as -35 and -10 have a negatively termed location?

A

This denotes their position relative to the transcription initiation site which is +1 They are upstream of the initiation site.

279
Q

What are consensus sequences of DNA?

A

Sequences of DNA which are not identical but are very similar and frequently have bases found at the same positions. They are often associated.

280
Q

When re consensus DNA sequences more likely to be transcribed?

A

When they are similar to the promoter region.

281
Q

Which sections of the gene will mutations in the -35 and -10 sequences affect most?

A

Promoter regions.

282
Q

What are footprinting experiments used for?

A

To determine the sites at which proteins bind to DNA.

283
Q

Describe the binding of RNA polymerase to DNA if the sigma in the RNA polymerase enzyme is not present.

A

Non-specific, low-affinity binding.

284
Q

What is the initial binding between RNA polymerase and a promoter region called and why?

A

Closed-promoter because DNA is not unwound.

285
Q

When is the sigma factor in RNA polymerase released and what does this cause?

A

It is released when RNA polymerase has travelled a short way down the DNA and produced a short piece of mRNA. This allows DNA polymerase to continue to the end of the gene.

286
Q

What happens to RNA and RNA polymerase when a termination signal is reached in prokaryotic DNA replication?

A

RNA is released from the RNA polymerase and RNA polymerase dissociates from the DNA template.

287
Q

How so stable stem loops lead to termination of transcription in prokaryotes ?

A

They disrupt the association between RNA and the DNA template. The presence of alot of adenine downstream of the inverted sequence also helps dissociate RNA from its template strand.

288
Q

What are the constituent sugars of lactose?

A

Glucose and Galactose

289
Q

What is the enzyme lactose permeate used for?

A

To transport lactose into cells.

290
Q

What is attenuation in prokaryotic DNA replication - general.

A

Regulates the expression of some genes by controlling the ability of RNA polymerase to continue elongation past certain points.

291
Q

How many chromosomes are prokaryotic genes located on?

A

1

292
Q

How many chromosomes are Eukaryotic genes located on?

A

Spread across many.

293
Q

What are the similarities between genes in the same operon?

A

They are all producing proteins with related functions.

294
Q

How many proteins does the Lac operon code for and what are these proteins involved in?

A

3 - they are enzymes involved in the fermentation of lactose. (The breakdown of lactose).

295
Q

Which site on the lac operon do repressor proteins bind to?

A

The lacO site

296
Q

What substance binds to inactivate the lac operon?

A

Allolactose

297
Q

Is polycistronic mRNA transcribed by the lac operon when lactose is or isn’t present ?

A

When lactose is present

298
Q

Is the lac operon repressor protein active the lactose is or isn’t in the cell.

A

When lactose is present.

299
Q

What is a DNA-binding motif?

A

A part of RNA polymerase that recognises a promoter.

300
Q

Why is most regulation of gene transcription controlled by inhibiting transcription?

A

Saves energy because only transcripts that will be used are produced.

301
Q

What is the part of RNA polymerase the recognises a promoter called?

A

A DNA-binding motif.

302
Q

What is the purpose of the ‘operator’ region of an operon?

A

Inducing transcription of genes which follow.

303
Q

When looking down at the major groove in a DNA helix, how may a G-C and a C-G base pair differ?

A

C-G pairs have a partially positive charge to the left and two electronegative groups to its right.

304
Q

How can enhancers activate a gene which is much further down the chromosome?

A

They collect activator proteins which promote transcription and are able to contact the initiator complex to stimulate transcription.

305
Q

How do nucleosomes influence gene expression in eukaryotes?

A

Transcription factors and RNA polymerase II cannot identify and bind to the promoter region.

306
Q

Give an example of how mRNA transcription can be increased Eukaryotes and how this works.

A

The Poly-A-Tail may be shortened, making it harder for RNA-digesting enzymes to bind to and destroy the transcript.

307
Q

Define mutations

A

A permanent change in the sequence of DNA that makes up out genome.

308
Q

Name the different classifications of mutations.

A

Point
Silent
Missense
Nonsense

309
Q

What is a point mutation?

A

One base is changed to another

310
Q

What is a silent mutation?

A

One base is changed to another but the triplet still codes for the same amino acid

311
Q

What is a missense mutation?

A

One base changes and the triplet codes for a different amino acid

312
Q

What is a nonsense mutation?

A

One base changes and produces a premature stop codon. This creates a trunkated version of the protein.

313
Q

What are the 2 types of base substitution and explain each.

A

Transitional - The base changes but are always purine or always pyrimidine.
Transversional - The base changes from purine to pyrimidine or vice versa.

314
Q

What is a frameshift mutation?

A

A small quantity of bases may be lost or altered in the DNA sequence. This causes the Fram of transcription to alter. This means that different triplet codons will be present and different amino acids will be different. This means the final polypeptide produced can be very different to what it should be.

315
Q

What are some of the consequences of a frame shift mutation?

A 
Loss of chromosomes
Gaining of chromosomes
Inversion of genetic material
Relocation of genetic material onto another chromosome
Deletion of sections of DNA
316
Q

What are somatic mutations?

A

Mutations that occur in any cells except gametes that aren’t heritable from parents.

317
Q

What are Germ-line mutations?

A

Mutations that occur in gametes that are heritable from parents.

318
Q

What the of mutations are heritable from parents?

A

Germ-line

319
Q

What type of mutations aren’t heritable from parents?

A

Somatic

320
Q

What type of mutations occur n gametes?

A

Germ-line

321
Q

How may DNA base mutations affect proteins and make them lose function?

A

May inhibit binding.
The protein may be preset in the incorrect location of the cell.
The protein may have a reduction in activity.
The whole protein may be lost and become no longer present in the cells.

322
Q

How many DNA base mutations negatively affect proteins by increasing their function?

A

Proteins may be expressed when they usually shouldn’t be and damage the function of the cell.
They may affect development of the cells if the mutations occur in promoter regions.

323
Q

Where must base mutations occur in non-coding DNA to have a functional effect.

A

Mutations may still show functional affect on non-coding DNA if they are present at splice sites or regulatory regions.

324
Q

How do base mutations occur during DNA replication?

A

DNA polymerase occasionally inserts incorrect nucleotide bases which leads to mutations.

325
Q

What is replication slippage and how does it cause mutations in DNA?

A

If a loop occurs in a DNA template strand, DNA polymerase can miss looped out nucleotides and small insertions and deletions may occur.

326
Q

What are tautomers of DNA bases?

A

Alternative chemical forms of nucleotide bases as a result of spacing of atoms and locations of bonds in the molecules.

327
Q

How do tautomeric shifts cause DNA mutations?

A

Tautomers alter the regular base pairing of DNA and create non-complimentary base pairing. The may lead to permanent mutations.

328
Q

What are the effects of non-replication DNA damage if not repaired immediately?

A

Will prevent replication of DNA and translation. May lead to death of cells.

329
Q

What is depurination of a DNA base?

A

A purine is lost and an apuric site is formed.

330
Q

What is Deamination of a DNA base?

A

Amino group in cytosine is covered to Uracil.
Or
An amino group in adenine is converted to hypoxanthine.

331
Q

What is oxidative damage to DNA?

A

Damage to DNA due to the by-products of normal cellular processes such as hydrogen peroxide, hydrogen radicals and superoxides.

332
Q

What are transposable elements in DNA and what are the effects of these regions?

A

DNA elements that are able to move within the genome. They can act as naturally occurring mutagens.
These cause DNA inversions, translocations, double-strand breaks and can cause chromosomal damage.

333
Q

What are the 2 mechanisms for the movement of transposable elements in DNA?

A

Cut and paste - one section of the genome is removed and inserted into another area of the genome.
Copy and paste - A copy of a genome section is inserted into another location on the genome.

334
Q

How does DNA polymerase prevent DNA mutations?

A

It proofreads and removes incorrectly inserted nucleotides in the 3’ to 5’ direction.

335
Q

What is mismatch repair of DNA?

A

If proofreading fails, mismatch repair is used to detect, cut and remove incorrectly inserted nucleotide sections using endonuclease and exonucleases.

336
Q

Outline the mismatch repair of DNA mechanism.

A

A mismach is detected in newly synthesised DNA.
The new DNA strand is cut and the mispaired nucleotides and its neighbours are removed using endo and exonucleases.
The missing patch is then replaced by correct nucleotides using DNA polymerase.
DNA Ligase seals the gap in the DNA backbone.

337
Q

What is direct reversal DNA repair?

A

Some damage can be directly undone by enzymes.

338
Q

What is Excision DNA repair?

A

Damage to one or few of DNA bases is often fixed by excision and replacement of the damaged region.

339
Q

What does excision mean?

A

To remove.

340
Q

What are the 2 methods of double-strand break repair of DNA repair?

A

Non-homologous end joining

Homologous recombination

341
Q

How does the homologous recombination method of double-strand break DNA repair work?
And when does this occur?

A

The break is recognised. The 5’ end is digested and the 3’ end is left overhanging. The 3’ end aligns with a complimentary sequence on the sister chromatin.
Occurs during late S phase or early G2 of the cell cycle.

342
Q

How does the Non-homologous end joining method of DNA double-stranded break repair work?

When does this occur?

A

The double-strand break is repaired using a complex of proteins and accessory proteins which bind the free ends and ligate them back together.

Occurs during G1 of the cell cycle before DNA replication.

343
Q

What is photoreactivation of DNA?

A

Two thymines are connected due to UV light.

344
Q

Why are double-strand breaks in DNA so harmful?

A

They result in chromosomal rearrangement which can lead to cancer and cell deaths.

345
Q

Where are the checkpoints in the cell cycle and what is the purpose of each?

A

G1/S - Allows DNA repair prior to DNA replication and ensures availability of materials for synthesis.
S phase - Delays replication to allow DNA repair before cell division.
G2/M - Final opportunity for DNA repair before cell division.

346
Q

What type of system is the E.Coli SOS repair system?

A

A regulon system

347
Q

What is a regulon ?

A

Multiple operons all under the control of the same regulatory processes. Components of the regulon can be anywhere in the genome.

348
Q

What is cellular senescence?

A

Irreversible cell cycle arrest

349
Q

How does the LexA repressor protein affect DNA replication? What organism is this present in?

A

Physically blocks DNA polymerase from binding to DNA in E.coli.

350
Q

How does the E.Coli SOS repair system work?

A

If DNA is damaged in E.Coli, RecA protein is activated and used to break down LexA. This means LexA doesn’ bind to the promoter region of the DNA and can no longer repress DNA replication. DNA is repaired.

351
Q

How does base excision repair work?

A

The incorrect DNA base is removed and replaced with the correct base using DNA polymerase. DNA ligase then re-seals the backbone.

352
Q

how does nucleotide excision repair work?

A

Repairs bulks of DNA which have been damaged by removing them and replacing them with non-faulty bases.

353
Q

What is the difference between base excision repair and nucleotide base excision repair?

A

Base excision - one one base

Nucleotide… - many bases.

Genetics (1 decks)

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