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Biology > Topic 8: Controlling gene expression > Flashcards

Topic 8: Controlling gene expression Flashcards

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1
Q

TRUE OR FALSE

ALL mutations are bad for organisms

A

FALSE

Not ALL mutations are bad. Sometimes they result in variation which allows for selection

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2
Q

What is a factor that increases the mutation rate called?

A

A mutagenic agent

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3
Q

What are the 6 main types of mutation?

A
  1. Translocation
  2. Inversion
  3. Duplication
  4. Deletion
  5. Addition
  6. Substitution
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4
Q

What are the 3 types of substitution mutation?

A

TYPES OF SUBSTITUTION

  1. Nonsense mutation (codes for stop codon)
  2. Mis-sense mutation (codes for a different AA)
  3. Silent mutation (same AA is coded for)
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5
Q

What is a translocation mutation?

A

When a whole section of bases within a gene is moved and inserted into a different chromosome

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6
Q

What is an inversion mutation?

A

When sections of bases are put in reverse order

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7
Q

What is a duplication mutation?

A

When sections of bases are copied (and thus repeated)

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8
Q

What type of substitution mutation is least harmful? Why?

A

A silent mutation. The same amino acid is coded for, so the same polypeptide, and this protein is also coded for

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9
Q

What type of substitution mutation is most harmful? Why?

A

Nonsense mutation. The substituted base (in the triplet) codes for a stop codon, so no more AAs are added to the polypeptide, so the tertiary structure is severely affected (reference to bonds)

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10
Q

When will an addition (/insertion) or deletion mutation not cause a frame shift?

A

If a multiple of 3 bases is inserted or deleted then the other amino acids coded for my the gene will not be frame-shifted

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11
Q

Why do some types of mutation not cause a change in the structure of the protein produced?

A
  • The genetic code is degenerate
  • Same amino acid may be coded for
  • Same H/ionic/disulphide bonds form in the same place
  • Protein forms same tertiary structure

(even if a different AA was coded for it MIGHT form the same H /ionic/ disulphide bonds, so still same structure)

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12
Q

TRUE OR FALSE?

All the cells in the body contain the same DNA and the same genes

A

TRUE
All the cells in the body contain the same genes
(Only some of the genes are expressed)

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13
Q

How do multicellular organisms have specialised cells?

A

The cells undergo differentiation to become specialised

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14
Q

What it mean when a gene is expressed?

A

The coded protein is produced in transcription and translation

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15
Q

What are totipotent cells?

A

Cells which have the capability to differentiate into ANY body cell

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16
Q

What are stem cells?

A
  • Undifferentiated, dividing cells
  • Can divide to form copies of themselves (replacement)
  • Only a few types in mature mammals can differentiate into other types of cell
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17
Q

Where are adult stem cells found?

A

Found in all body tissues

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18
Q

What are adult stem cells?

A
  • Stem cells which are specific to the tissue/organ where produced
  • Used to maintain + repair tissues throughout life
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19
Q

What are the 4 types of stem cell?

A
  1. Totipotent
  2. Pluripotent
  3. Multipotent
  4. Unipotent
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20
Q

Where are totipotent cells found?

A

In Zygote early stages

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21
Q

Where are pluripotent cells found?

A

Embryo

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22
Q

Where are multipotent cells found?

A

Mature mammals

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23
Q

Where are unipotent cells found?

A

Mature mammals

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24
Q

What can totipotent cells differentiate into?

A

All body cells

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25
Q

What can pluripotent cells differentiate into?

A

All body cells except the placenta + umbilical cord

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26
Q

What can multipotent cells differentiate into?

A

A limited number of specialised cells

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27
Q

What can unipotent cells differentiate into?

A

A single type of cell (tissue specific)

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28
Q

How can colonies of pluripoent cells be made specific?

A

A differentiation factor is added to differentiate the pluripotent cells into a specific type of cell

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29
Q

What are induced pluipotent cells (iPS)?

A
  • Pluripotent cells produced from adult cells
  • Can divide into unlimited numbers (self-renewal)
  • Can be used to treat human disorders
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30
Q

How can induced pluripotent cells be produced?

A
  • Body cells genetically altered in the lab
  • Induces genes and transcription factors to express themselves

Basically turns on and off the necessary genes

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31
Q

Name 3 advantages of induced pluripotent cells.

A
  1. No immune response because they are the patients’ own cells
  2. Stem cells can be obtained from adult cells
  3. Can produce all types of cell
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32
Q

Why are induced pluripotent stem cells more ethically suitable than embryonic stem cells?

A

iPS are produced from adult cells, so embryonic cells are not used

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33
Q

Give two characteristics of stem cells

A
  1. Capable of self-renewal

2. Can differentiate into any cell

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34
Q

TRUE OR FALSE?

Mature plants have many totipotent cells

A

TRUE

Mature plants have many totipotent cells which can develop into any cell type

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35
Q

What regulates the differentiation of totipotent cells in plants?

A

Growth regulators

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36
Q

Name 4 features of growth regulators in plants.

A
  1. Have a range of effects on plant growth
  2. The effects depend on the concentration of growth factors
  3. The same conc affects different types of tissue in different ways
  4. The effect of a growth factor can be modified by the presence of another
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37
Q

Why can’t xylem differentiate into other cells?

A

Xylem is dead tissue, so it cannot differentiate into other cells

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38
Q

What do growth regulators enable plants to do?

A

If placed in a growth medium, plants cells from a single plant will develop into new plants

Called IN VITRO DEVELOPMENT

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39
Q

What is in vitro development?

A

When growth regulators are used to create cloned plant tissue (a tissue culture)

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40
Q

What will plants derived from tissue culture share?

A

The same genetic material

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41
Q

What is the term for undifferentiated plant cells?

A

Callus

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42
Q

How do cells differentiate?

A

Certain genes must be switched on (expressed), whilst others are switched off

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43
Q

How are genes expressed (or not)?

A

Transcription and translation are regulated

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44
Q

What is transcription (basic)?

A

DNA -> mRNA

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45
Q

What is a transcription factor?

A
  • A protein/ molecule that moves from cytoplasm to DNA
  • Binds to a specific gene
  • Allowing / blocking protein production
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46
Q

How do transcription factors bind to DNA?

A
  • Specific DNA binding site
  • Complementary to the specific shape of a DNA base sequence
  • Binds to a PROMOTER REGION
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47
Q

What do transcription factors enable?

A

Enables RNA polymerase to bind to DNA, allowing or preventing transcription

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48
Q

What is an example of a molecule activating transcription factors?

A

Oestrogen

Has specific functional site which can bind to a receptor on a TF so the TF changes shape to become active

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49
Q

What are the proteins that Eukaryotic DNA associates with called?

A

Histones

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50
Q

What is the DNA associated with histones called?

A

Chromatin

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51
Q

What is highly-coiled DNA and histones called?

A

Heterochromatin

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52
Q

What is loosely-coiled DNA and histones called?

A

Euchromatin

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53
Q

Why can DNA be transcribed when DNA and histones are loosely associated (euchromatin)?

A

Transcription factors are able to bind to the promoter region of DNA

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54
Q

What is epigenetics?

A

A process by which environmental factors can cause heritable changes in gene function without changing the base sequence of DNA

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55
Q

What does Methylation cause? (4 points)

A
  • DNA nucleotides pack together tightly
  • Creates heterochromatin
  • TFs cannot bind
  • Genes are not transcribed or translated
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56
Q

What does Acetylation cause? (4 points)

A
  • DNA nucleotides are loosely packed together
  • Creates euchromatin
  • TFs can bind to the DNA
  • Genes are transcribed and translated
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57
Q

Does the DNA sequence change in the epigenome?

A

No

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58
Q

What attaches to DNA to cause methylation and acytylation?

A

Chemical tags causing DNA to become more/less associated with histones

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59
Q

What is it called when inactive genes are kept tightly packed in epigenetics?

A

Epigenetic silencing

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60
Q

What does the acetylation of histones actually do?

A

Masks the +ve charge of histones (makes them -ve) so less attracted to -vely charged DNA

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61
Q

What factors influence the epigenome?

A

The accumulation of signals in the foetus and during a lifetime

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62
Q

Where do epigenetic signals come from in the foetus?

A

Nutrition provided by the mother (eg smoking)

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63
Q

Where do epigenetic signals come from during life?

A
  • Environment (diet/stress etc)

- Signals within the body (hormones)

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64
Q

Can epigenetic tags be inherited?

A

Not many

  • Tags are erased in gametes
  • Some epigenetic tags escape the process and become inherited by the next generation
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65
Q

Considering epigenetics, why is reproductive cloning difficult?

A

All epigenetic tags are inherited, so some genes are not able to be expressed because TFs cannot bind to promoter regions, so transcription and translation do not occur

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66
Q

How can epigenetics trigger cancers?

A
  • Promoter regions on some tumour suppressor genes become hyper-methylated
  • The promoter region becomes inactive
  • No transcription of tumour surpressor occurs
  • Cell division increases

(can also be reduced methylation of oncogenes, same effect)

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67
Q
  1. How can drugs be used to counteract epigenetic changes which could cause cancer?
  2. What is a disadvantage of this?
A
  1. Drugs can target enzymes involved in histone acetylation and DNA methylation
  2. If not carefully administered to target cancerous cells then the risk of cancer could increase in other tissues
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68
Q

How can epigenetic tags be used in medical diagnosis?

A
  • The levels of DNA methylation and histone acytylation can allow the cancer risk to be identified
  • Treatment can start sooner, so a better prognosis
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69
Q

In epigenetics, where does methylation occur?

A

On DNA itself

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70
Q

In epigenetics, where does acetylation occur?

A

On the histones in chromatin

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71
Q

Where does transcription take place?

A
  • pre-mRNA produced in the nucleus
  • pre-mRNA is spliced to remove introns
  • mRNA leaves the nucleus vias nuclear pore
  • mRNA ready for translation
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72
Q

Where does translation take place?

A

In ribosomes on he rough ER or cytoplasm

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73
Q

What is siRNA?

A
  • Small Interfering RNA
  • Inhibits the production of a gene by translation
  • Breaks down mRNA before info is translated into a polypeptide

Regards interfering with gene expression

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74
Q

How does siRNA break mRNA? (4 points)

A
  • Enzyme cuts large double-standed sections of RNA into siRNA
  • One stand of the siRNA combines with an enzyme
  • siRNA guides the enzyme to mRNA with comp base pairing
  • Enzyme mRNA into smaller sections
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75
Q

What effect does siRNA have on protein synthesis? (3 points)

A
  • mRNA is cut by enzyme associated with siRNA
  • mRNA unable to be translated into the correct polypeptide
  • The gene is not expressed
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76
Q

What is cancer?

A

A group of diseases caused by damage to genes that regulate mitosis and the cell cycle
Causes uncontrolled cell growth (tumour)

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77
Q

How many cells cause cancer?

A

Just one which subsequently divides

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78
Q

What are the two types of tumour?

A

Benign and malignant

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79
Q

What is a benign tumour?

A

A non-cancerous tumour

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80
Q

What is a malignant tumour?

A

A cancerous tumour

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81
Q

What are some key characteristics of malignant tumours? (4 points)

A
  • Grow rapidly and aggressively
  • The cell nucleus is distinctive
  • Cause secondary tumours
  • The tumours are not surrounded by a capsule, so have finger-like projections
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82
Q

What two mutations cause a cancer cell?

A
  1. Initial mutation leads to uncontrolled mitosis in cells

2. Mutation in decedent cells causes subsequent cells to become abnormal

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83
Q

What two genes control cell division?

A

Proto-oncogens and tumour suppressor genes

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84
Q

What the normal function of proto-oncogens?

A

Stimulates cell division

Like an accelerator pedal in a car, it controls how fast the cell cycle goes

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85
Q

What is the normal function of tumour suppressor genes?

A

Slow down cell division and program cell death

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86
Q

How do proto-oncogens function normally?

A
  • Growth factor binds to receptor protein
  • Relay protein is released
  • Relay proteins cause genes needed for DNA replication in the nucleus to be switched on
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87
Q

What are oncogens?

A

Mutations of proto-oncogens which cause oncogens to be permanently switched on

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88
Q

What are the 2 reasons for an oncogene to become permanently activated?

A
  1. Receptor protein on the cell surface membrane can be permanently activated - no effect with growth factors
  2. Growth factors may be produced in excessive amounts
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89
Q

What are the possible consequences of a mutation to a tumour suppressor gene? (4 points)

A
  • The gene becomes inactive
  • Cell division increases
  • Cells become structurally/functionally different +dies
  • Some cells survive and clone by mitosis = tumour
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90
Q

How many mutated alleles do you need to trigger cancer with tumour suppressors?

A

2

Even if one tumour suppressor gene is mutated, faulty, the other will still work and regulate cell division

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91
Q

How many mutated alleles do you need to trigger cancer with oncogenes?

A

1

A mutation to one allele will still cause the gene to be expressed and to have an effect

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92
Q

What can be done to prevent, treat and cure cancer?

A
  • Preventing the expression of oncogenes

- Introducing tumour suppressor genes into cancerous cells

93
Q

What is an example of a molecule that activates transcription factors?

A

Oestrogen

94
Q

What is a genome?

A
  • The complete set of genetic info in a organism

- Provides all the info an organism needs to function

95
Q

What are the 3 aims of genome projects?

A
  1. Determines the entire nucleotide sequence of organisms
  2. Maps the DNA sequence of all genes on an organism
  3. Maps the genes to individual chromosomes
96
Q

How many genes do Homo sapiens have?

A

20,000 - 25,000

97
Q

How many base pairs to Homo sapiens have?

A

3 billion

98
Q

What % of base pairs code for proteins in humans?

A

1%

99
Q

What is bioinfomatics?

A

The science of collecting + analysing complex biological data using algorithms + maths

100
Q

What charge does DNA have?

A

Negative charge

101
Q

In gel electrophoresis, what direction does DNA move?

A

From negative to positive charges because DNA is negatively charged

102
Q

Which DNA fragments move furthest in gel electrophoresis?

A

The shortest fragments

103
Q

Why do the shortest DNA fragments move the furthest in gel electrophoresis?

A

The fragments can move through the gel granules more easily, so move through the gel faster and thus cove more distance in a given time

104
Q

How do you measure the size of DNA fragments in gel electrophoresis?

A

Using a ladder of DNA fragments of known lengths

105
Q

What was the name of the original process used to sequence DNA?

A

Sanger Sequencing

106
Q

What is a primer?

A
  • A short piece of DNA that binds to template DNA
  • Gives something for DNA polyerase to join onto to start a new chain

(used in Sanger Sequencing)

107
Q

Why are new methods of DNA sequencing better?

A
  • Less labour intensive
  • Faster turnaround
  • Longer DNA strands can be sequenced
108
Q

What are the 3 steps involved in whole genome shotgun sequencing?

A
  1. DNA cut into short sequences
  2. Computer algorithms align overlapping segments
  3. Assembles the entire genome
109
Q

What are Single Nucleotide Polymorphisms (SNPs)?

A
  • Single base sequences in the genome associated with some disorders
  • > 1.4 million SNPs in the human genome
110
Q

What is a proteome?

A

All the proteins produced in a given cell/organism at a given time, under specific conditions

111
Q

Why is determining the proteome easier in prokaryotes>

A
  • One circular piece of DNA
  • DNA unassociated with histones
  • No introns
112
Q

Why can sequencing genomes of pathogens help cure diseases?

A
  • Identifies the DNA sequence of antigens on pathogens

- Allows vaccines of the complementary antibody to be produced

113
Q

TRUE OR FALSE?

Introns are found are found between genes?

A

FALSE
Introns are repeated bases within genes

VNTRs are repeated base sequences found between genes

114
Q

What is a gene?

A

A section of DNA that codes for a polypeptide or a functional RNA (tRNA and rRNA)

115
Q

Why is the genetic code said to be universal?

A

The same triplet codes for the same amino acid in all organisms

116
Q

What is recombinant DNA?

A

Combining DNA from 2 different organisms

117
Q

What is a transgenic organism?

A

An organism that has had its genome modified

Also called Genetically Modified Organism (GMOs)

118
Q

What does recombinant DNA technology do? (3 points)

A
  • Transfers DNA from one organism/species to another
  • The gene is translated in the recipient
  • Due to the universal nature of DNA
119
Q

What does IN VIVO mean?

A

Inside a living organism

120
Q

What does IN VITRO mean?

A

In glass (not a living organism)

121
Q

What are the 5 basic stages of recombinant DNA?

A
  1. Isolation of gene
  2. Insertion of the gene into a vecto
  3. Transformation of gene + vector into a host
  4. Identification of the gene that has been taken up by the host using gene markers
  5. Growth/cloning of cells
122
Q

Why can’t eukaryotic genes be successfully transcribed + translated in prokaryotes?

A
  • Eukaryotic genes contain introns
  • Prokaryotes lack enzymes to remove introns
  • The protein would thus contain additional AAs and would not fold correctly (BONDS + STRUCTURE)
123
Q

How can the effect of introns in recombinant eukaryotic DNA (into Prokaryotes) be overcome?

A

Using reverse transcriptase on mRNA (post-splicing)

124
Q

What is REVERSE transcription?

A

mRNA -> complementary DNA (cDNA)

125
Q

What is complementary DNA (cDNA)?

A
  • DNA that does not contain introns
  • Complementary to mRNA
  • Made from mRNA using reverse transcriptase
126
Q

What organisms use reverse transriptase?

A

RNA Viruses (used in virus replication)

127
Q

What are restriction endonucleases?

A

A group of enzymes which cut DNA at specific base sequences called recognition sites

128
Q

What are restriction endonucleases used for in recombinant DNA?

A

Used to cut desired genes from DNA of one organism in order to insert it into the DNA of another

129
Q

What are the two types of ‘end’ cut with restriction enzymes?

A

Blunt- and sticky-ends

130
Q

What are palindromic sequences?

A

Sequences on two single strands of DNA which are read the same backwards

Eg
ACGT on one strand
TGCA on the other

131
Q

What is a sticky end?

A
  • Formed when restriction endonuclease cuts at different positions on two DNA strands
  • Leaves each section with a single-stranded part complementary to the other
132
Q

What is a blunt end?

A

When a restriction enzyme cuts at the same position on each strand

133
Q

Why can you join together two DNA fragments from different organisms that have both been cut by the same sticky-end restriction endonuclease?

A

The single strands of exposed bases are complementary because the restriction endonuclease has a specific, unique shape

134
Q

What enzyme is used in recombinant DNA to join together two adjacent nucleotides joined by sticky ends?

A

DNA LIGASE (not polymerase because only one phosphodiester bond is being formed)

135
Q

How does a gene machine artificially produce a gene? (5 steps)

A
  1. Computer designs a series of DNA sequences
  2. Small single-stranded sequences assembled by adding one nucleotide at a time
  3. Small sequences combined to create a gene
  4. Gene replicated using PCR
  5. Gene inserted into vector (using restriction endonucleases + DNA Ligase)
  6. Vector transferred to a host cell to be replicated
136
Q

Why are gene machines useful?

A
  • Sequence of DNA can be produced in a short amount of time
  • The genes are artificial and contain no introns
  • No introns = transcription + translation in prokaryotes
137
Q

What do genes need to function effectively?

A

A promoter region and a terminator region

138
Q

What are promoter regions?

A

The specific sequence of DNA nucleotide bases where RNA polymerase and transcription factors bind, allowing the production of mRNA by transcription

139
Q

What are terminator regions?

A

The specific sequence of DNA nucleotide bases where transcription factors disengage from DNA, stopping transcription

140
Q

What bonds does RNA polymerase form between nucleotides?

A

Phosphodiester bonds

141
Q

What needs to be added to a DNA fragment before insertion into a vector?

A
  • Promoter at the front so RNA polymerase + TFs bind and produce mRNA
  • Terminator at the end of the gene to stop trnascription
142
Q

What does a restriction endonuclease do?

A

Cuts DNA at specific palindromic recognition sites

143
Q

Why are sticky ends better than blunt ends when joining DNA strands together?

A
  • Same restriction endonuclease used (specific structure)
  • The ends of the two fragments from the two species will be complementary
  • H bonds will form between the complementary bases
144
Q

What is a vector in recombinant DNA technology?

A

A DNA molecule that carries foreign DNA into a cell where it can replicate or be expressed

Example: Bacterial plasmid

145
Q

What is the advantage of inserting recombinant plasmids into host cells?

A

Every time the bacteria containing the plasmid replicate by binary fission, the plasmid will also replicate

146
Q

What is it called when DNA is inserted into host cells?

A

Transformation

147
Q

How can transformation of bacteria and recombinant plasmids occur?

A

Heat shock treatment

  • Bacteria mixed with calcium ions to make permeable
  • Chilled on ice
  • Warmed to 42 degrees
148
Q

What is an alternative method, besides heat shock, of transformation? (recombinant DNA technology)

A

Electroporation

149
Q

What is the purpose of heat shock / electroporation in transformation?

A

Makes the bacteria more permeable so the recombinant plasmid is taken up (and can thus be replicated or expressed in the bacteria)

150
Q

Why do only some bacteria possess DNA fragments after transformation? (3 points)

A
  • Only some take up the recombinant plasmid
  • Some plasmids self-ligate (recreating the original plasmid)
  • DNA fragments may join together to make own plasmid
151
Q

By what process do bacterial cells divide?

A

Binary fission

152
Q

How can transformed bacteria be identified? (recombinant DNA)

A

Using genetic markers to identify which bacteria contain the plasmid with the desire gene

153
Q

What are 3 types of genetic markers?

A
  1. Enzymes
  2. Antibiotic resistance genes
  3. Florescence genes
154
Q

How were marker genes previously used?

A
  • Desired gene inserted into one marker gene (antibiotic resistance gene) using comp restriction enzymes, sticky ends and ligase
  • The antibiotic is added and the bacteria with the desire genes die (as gene is not intact)
155
Q

How are marker genes now used?

A
  • The antibiotic resistance marker gene is connected directly to the gene of interest
  • Only the bacteria which survive the antibiotic have the desired gene
156
Q

When growing bacteria in a culture to obtain desired genes, what should be done? Why?

A
  • The bacteria should be diluted
  • Allows the bacterial solution to spread out on the agar jelly
  • Allows room for each individual bacteria to produce a clear colony
157
Q

What will happen if a desired gene is inserted directly into a fluorescence gene? (Recombinant DNA tech)

A
  • When UV light is shined onto the bacterial culture the bacteria which are not glowing will contain the desired gene
  • The fluorescence gene will be split so no longer functions (as cannot be transcribed + translated)
158
Q

Why is using fluorescent gene markers better than using antibiotic gene markers when identifying recombinant bacteria?

A
  • Unlike with antibiotics, the bacterial cells with the desired gene are not killed
  • Thus no need for REPLICA PLATING
  • So faster
159
Q

What is a method of in vivo gene cloning?

A

Using bacterial plasmids and transforming bacteria to replicate the desired gene

160
Q

What is a method of in vitro gene cloning?

A

The Polymerase Chain Reaction (PCR)

161
Q

What 5 components are needed to replicate DNA in vitro (PCR)?

A
  1. DNA fragment to be copied
  2. Pair of primers
  3. DNA nucleotides in excess
  4. Thermostable DNA polymerase
    5 Thermocycler
162
Q

What are DNA primers?

A

Short lengths of DNA that are complementary to the 3’ end of each DNA strand

163
Q

Why are DNA primers needed for PCR?

A
  • Polymerase can only add nucleotides to an existing strand
  • Gives polymerase something to join new nucleotides to
  • Prevents the separated strands from rejoining
164
Q

Why is a heat stable DNA polymerase used in PCR?

A

Ordinary DNA polymerase (enzyme) will denature in the high temps used in PCR

165
Q

What is a thermocycler?

Where is it used?

A

A computer-controlled machine which varies temperatures precisely over a period of time

Used in the polymerase chain reaction (PCR)

166
Q

What are the 3 steps of the polymerase chain reaction?

A
  1. Separation of DNA strands
  2. Annealing of primers
  3. Synthesis of DNA
167
Q

At what temperatures do the 3 steps of the polymerase chain reaction take place?

A
  1. Separation of DNA strands
    95C
  2. Annealing of primers
    50-60C
  3. Synthesis of DNA
    72C
168
Q

What takes place during the first step (separation of DNA strands) in PCR?

A
  • H bonds break in high temp (95C)
  • Strands separate
  • Each strand acts as a template
169
Q

What takes place during the second step (annealing of primers) in PCR?

A
  • Primers join to complementary exposed bases at the end of the DNA fragment
  • Provide starting sequence of DNA polymerase
  • Prevents original strands rejoining
170
Q

What takes place during the third step (synthesis of DNA) in PCR?

A
  • Complementary DNA nucleotides make H bonds with exposed bases on each template strand
  • Beginning at the primer, DNA polymerase joins nucleotides by phosphodiester bonds along one of the template strands, forming 2 copies
171
Q

How are hydrogen bonds between complementary bases broken in the polymerase chain reaction?

A

H bonds broken by heat

172
Q

How are hydrogen bonds between complementary bases broken in DNA replication?

A

H bonds broken by DNA helicase

173
Q

Are primers (supposedly) needed in DNA replication?

A

No (although technically they do)

174
Q

Why is PCR useful in forensic science?

A

Allows lots of DNA to be amplified from a small amount extracted at a crime scene

175
Q

What happens to the amount of DNA in a PCR machine each time it completes one cycle?

A

The amount doubles

176
Q

What are the 4 advantages of in vitro gene cloning (PCR)?

A
  1. Makes lots of DNA from a small amount
  2. Faster than conventional methods
  3. Allows for forensic analysis
  4. Cells do not need to be cultured
177
Q

What are the 4 advantages of in vivo gene cloning (plasmids in bacteria)?

A
  1. Desired gene can be easily transferred once in a vector to another organism
  2. Only the gene with complementary sticky ends is cloned, so less risk of contamination
  3. Accurate replication in organisms
  4. Can clone specific genes
178
Q

What are the 2 disadvantages of in vitro gene cloning (PCR)?

A
  1. Risk of contamination (errors) - the contaminated DNA is also amplified
  2. Less accurate than in vivo gene cloning
179
Q

What are somatic cells?

A

Any cell other than reproductive cells

180
Q

What are germ cells?

A

Reproductive cells/gametes

181
Q

Why are genes isolated and cloned using recombinant DNA technology?

A

Allows genetic disorders to be treated

182
Q

What is somatic cell therapy?

A
  • Targets specific tissues (eg lungs)
  • The altered gene is not present in other cells
  • Cells are constantly replaced by mitosis, so treatment needs to be repeated
183
Q

What is germ cell therapy?

A
  • Occurs in fertilised eggs
  • Results in all cells of organisms possessing the gene
  • Faulty gene not passed onto future generations

CURRENTLY PROHIBITED

184
Q

Why is the risk of contamination very low in vivo gene cloning?

A
  • The gene and the plasmid are both cut by the same restriction endonuclease which is specific to the structure of complementary bases
  • Only the desired gene is taken up
185
Q

Why is in vivo gene cloning better for transforming genes into living organisms?

A
  • Uses vectors
  • Transformed plasmids can be used to deliver the gene to another organism
  • The basics of gene therapy
186
Q

What type of mutation causes cystic fibrosis?

A

A deletion mutation of 3 adenine bases

187
Q

Why are viruses suitable for gene therapy?

A
  • Specifically target certain cells with specific receptors
  • Adapted to insert DNA into host cells
  • Host cells produce viral proteins by transcription + translation
188
Q

How can a virus be used to treat genetic respiratory disorders (CF)?

A
  • The desired gene is inserted into harmful gene
  • Harmful gene becomes inactive
  • The desired gene is inserted into the affected cell
189
Q

Why are viruses used in gene therapy grown in a human cell culture?

A

The viruses need a cellular host to replicate as the host possesses the enzymes + nucleotides required for replication

190
Q

Why is using a virus as a method of gene therapy risky? (2 reasons)

A
  • Viruses could still cause infections by recovering the ability to cause disease
  • The patient may develop immunity to the virus (as it is a foreign body), so antibodies may be produced for a secondary response to future treatment
191
Q

What is an alternative method of gene therapy to the use of viruses?

A

Liposomes

192
Q

Why are liposomes used in respiratory gene therapy?

A

They are made from lipids so fuse with the phospholipid bi layer and offload the desired gene

193
Q

What are 3 disadvantages of gene therapy?

A
  1. If viruses are used they could become harmful
  2. The genes inserted are not always expressed
  3. Only useful for diseases caused by a single faulty gene (i.e. recessive alleles)
194
Q

Why does somatic gene therapy have to be repeated?

A
  • The inserted gene is not incorporated into chromosomes

- When the cell replicates the gene is not copied

195
Q

Why does gene therapy become less effective with successive treatments?

A
  • Virus/liposomes trigger an immune response
  • Subsequent treatments also trigger an immune response which is of greater magnitude + speed
  • Antibodies coat virus/liposomes, preventing the desired infetion of target cells
196
Q

Why is it difficult for genetic therapy to be used to treat genetic diseases caused by multiple genes?

A
  • All the corrected genes need to be expressed in the same cell
  • Low probability of this
197
Q

What is a DNA probe?

A

A short single-stranded length of DNA that has a label attached to make it identifiable

198
Q

Name two examples of DNA probes used

A
  1. Radioactively-labelled probes

2. Fluorescently labelled probes

199
Q

What is a DNA probe made of?

A
  • A short sequence of DNA
  • Complementary nucleotide base sequence of gene of interest
  • Label added
200
Q

How is DNA to be screened using a probe broken into single strands?

A

Using an alkali to break the H bonds between opposite complementary bases

201
Q

How can short, known sequences of DNA be made (eg for use as a probe)?

A

Using a gene machine

202
Q

How can multiple copies of a DNA probe be made?

A

Using PCR

203
Q

How does a DNA probe bind to a screened DNA fragment?

A
  • If the gene being screened for is present
  • The probe will bind to this gene
  • By complementary base pairing
204
Q

Why is screening of tumour suppressor genes important?

A
  • Mutations to both tumour suppressor alleles could make the tumour suppressor gene inactive
  • Could cause a tumour
  • Screening allows for hetrozygous individuals to be identified
205
Q

What is personalised medicine?

A

A method adopted by doctors which allows advice and healthcare to be prescribed based on a patients genotype

206
Q

What is the main benefit of personalised medicine?

A

Allows the most effective drug to be given to a patient so drug selection and dosage is tailored.

This saves money and sometimes prevents harm

207
Q

What is genetic counselling?

A

Advice given to patients or relatives at risk from an inherited disorder

208
Q

What sort of advice do genetic counsellors give?

A
  • Info in consequences + nature of the disorder
  • Probability of developing/inheriting it
  • Possible options for family planning
209
Q

What is DNA gel electrophoresis?

A

A technique used to separate DNA strands according to their length

210
Q

How can the lengths of DNA be calculated from gel electrophoresis?

A

Run a DNA ladder on the gel which indicates fragments of known sizes

211
Q

What is genetic fingerprinting?

A

A diagnosis tool used by forensic and medical scientists

212
Q

Is the DNA of EVERY individual unique?

A

No EVERY individual. Every individual except identical twins

213
Q

What are Variable Number Tandem Repeats (VNTRs)?

A

Non-coding parts of DNA found BETWEEN GENES

214
Q

What is the difference between introns and VNTRs?

A

Introns are non-coding parts of DNA found WITHIN genes

VNTRs are non-coding parts of DNA found BETWEEN genes

215
Q

How many VNTRs between the same gene do different people have?

A

Different numbers, unique to individuals

216
Q

Why are VNTRs useful?

A

Each individual has a different number of VNTRs between the same genes, so a unique “bar code” exists

This is a genetic fingerprint

217
Q

How can DNA VNTRs be isolated for genetic fingerprinting?

A

With the use of restriction endonucleases

218
Q

Which VNTR moves the furthest in gel electrophoresis?

A

The shortest

219
Q

Which specific part of DNA is negatively charged?

A

The phosphate group

220
Q

Why are DNA fragments (VNTRs) transferred onto a nylon membrane in gel electrophoresis?

A

The gel is fragile

221
Q

What are the 7 steps of gel electrophoresis?

A
  1. DNA extracted from a sample and cut into fragments using restriction endonucleases
  2. Fragments added to electrophoreisis gel and separates according to size (shortest furthest etc)
  3. DNA fragments transferred onto nylon membrane
  4. DNA made single stranded (heat/alkali)
  5. Radioactively-labelled DNA probes are added
  6. Membrane put onto x-ray film
  7. X-ray film develops with distinctive dark bands
222
Q

Which type of cell contains no nucleus?

A

Red blood cells

223
Q

Why can’t red blood cells be used for genetic fingerprinting?

A

No nucleus, so no genetic material (DNA) is stored to be used

224
Q

What is the difference between a gene machine and PCR?

A

Gene machine makes short sequences of DNA

PCR makes multiple copies of genes (long sequences)

225
Q

In gel electrophoresis, why is the nylon membrane washed after adding probes and before exposing to x-ray film?

A

It washes away any unbound DNA probes so that they do not contaminate the x-ray film so no false positive results

226
Q

Give 5 uses of genetic fingerprinting

A
  1. Forensics
  2. Paternity tests
  3. Archaeology
  4. Animal population studies
  5. Organ donor selection
227
Q

What are ethics?

A
  • Narrower than social morals

- A set of standards set up by a society to regulate behaviour

228
Q

What are social issues?

A
  • Relates to human society and organisation

- Concerns the mutual relationship of human beings, their independence and cooperation to benefit all

229
Q

What is required with recombinant DNA technology?

A

Evaluations

Must revise this briefly (page 542)

Biology (10 decks)

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