Gene Therapy. Flashcards
1
Q
Define gene regulation?
A
The ability for a gene to be turned on or off.
2
Q
Define a somatic cell?
A
Any cell within the body that is not a sex cell.
3
Q
Define transfection?
A
The process of deliberately inserting genetic material into a eukaryotic cell.
4
Q
Define a transgene?
A
A genetically modified gene.
5
Q
What is gene therapy?
A
A molecular biology tool that can be used to treat disease by modifying genes within the patient.
6
Q
What kind of diseases can be treated via gene therapy?
A
Genetic and acquired diseases.
7
Q
What process does gene therapy usually involve?
A
Inserting a normal gene directly into a cell.
8
Q
How does inserting a normal gene into a cell help correct a genetic disease?
A
The normal gene will produce normal gene products and this can correct or prevent a pathological process.
9
Q
How is normal DNA inserted into a malfunctioning cell?
A
Normal DNA is isolated from a normal cell and is then packaged into a vector and inserted into the cell.
10
Q
What vector is often used for gene therapy?
A
A modified virus.
11
Q
What is germline gene therapy?
A
It involves inserting a transgene into an unfertilised egg.
12
Q
What are the 3 major techniques that can be used to insert transgenic genes into an organism?
A
Germline therapy.
Germinal therapy.
Somatic therapy.
13
Q
What happens in germline therapy after the transgene has been inserted into an unfertilised egg?
A
The egg can be fertilised allowing the egg cell to divide and form new cells, all of which contain the transgene.
14
Q
What is germinal therapy?
A
It inserting a transgene into a blastocyst.
15
Q
In germinal therapy, which cells of the blastocyst will exhibit the DNA from the transgene?
A
A blastocyst is multicellular and only a single cell will take up the DNA of interest.
Therefore, only cells that are formed from this particular cell will display the transgene.
16
Q
Does germinal therapy allow for all the cells of the blastocyst to exhibit the transgene?
A
No.
This method only allows for the transgene to be present in some of cells.
17
Q
What kind of structure is created by germinal therapy?
A
A mosaic gonad.
18
Q
Why is a mosaic gonad created by germinal therapy?
A
Because the transgene is not present in every cell in the body.
19
Q
Are the genetic changes that arise from germline and germinal gene therapy heritable?
A
Yes.
20
Q
Can the traits that arise from transgenic DNA be passed down to offspring?
A
Yes.
21
Q
What does the heritabloe nature of transgenic DNA mean?
A
It means that any negative traits that have been corrected will not be transmitted to offspring.
22
Q
Why has germline and germinal gene therapy not been carried out on humans?
A
As they both have issues over the ethics of inserting foreign genes into unwilling participants.
23
Q
What is somatic gene therapy?
A
It involves introducing a transgene into a somatic cell that has been affected by disease.
24
Q
What happens in somatic gene therpay once the transgene has been incorporated into the somatic cells genome?
A
The cell will replicate the new genetic material every time it divides.
This creates a number of cells that do not exhibit the disease and this allows for the disease to be cured.
25
Are the genetic changes that arise due to somatic therapy are heritable?
No.
26
The effects of somatic gene therapy are confined to who?
To the patient.
27
Will the effects of somatic gene therapy affect every cell within the body?
No.
28
What must happen with somatic gene therapy if the effects are to be long lasting?
The process may have to be repeated at in the future for the effects to be maintained.
29
What can the process of using somatic therapy to insert the DNA of interest into a cell be thought of as?
As infecting a cell with new DNA.
30
What are the 2 outcomes that can occur after using somatic gene therapy to infect a cell?
The creation of an integrated gene.
The creation of an episomal gene.
31
What is an intergrated gene?
A gene that is incorporated into the genome of the cell.
32
What is an episomal gene?
A gene that is not incorporated into the cellular DNA and is left in the cytoplasm of the cell.
33
The creation of what kind of genes are most desirable in somatic gene therapy?
The creation of integrated genes, as these cells will utilise the gene of interest to correct any cellular abnormalities.
34
What happens when somatic cells with an intergrated gene divide?
They will copy the gene of interest and this allows creates new cells that are free of abnormalities.
35
Will the abnormalities be corrected in cells that contain episomal genes?
No, as these cells can not utilise the gene of interest and this means that cellular abnormalities will persist.
36
How can the abnormalities cells with episomal genes be corrected?
By inserting a new gene of interest into the nucleus.
37
When cells containing episomal genes divide, will they copy the episomal gene?
No.
38
What is in vivo gene therapy?
Where normal genes are inserted into the DNA of human cells whilst they are in the body.
39
What is ex vivo gene therapy?
Where cells are removed from the patient and new genes are transferred into these cells.
The modified cells are placed onto growth media where they can replicate and form a collection of modified cells.
These modified cells can then be inserted into the patient.
40
During ex vivo gene therapy, how can scientists tell if the gene of interest has been inserted into the cells in growth media?
Via selectable markers that can show which cells have taken up the modified DNA.
41
What happens in in vivo gene therapy after the modified DNA has been inserted into cells?
The cells will replicate and create new cells that contain normal genes.
This allows for normal cells to replace a population of damaged or defective cells.
42
What is involved in the process of gene augmentation therapy?
It involves inserting a normal gene into a non-specific location within the genome.
43
What is gene augmentation therapy used for?
To replace a non-functional gene with a newly inserted normal gene.
44
What can gene augmentation therapy be used to treat?
Inherited genetic disorders that are caused by the loss of function of a gene.
45
What characteristic must a genetic disorder have if its effects are to be cured by gene augmentation therapy?
The condition must be reversible or this strategy will have no effect on the patient.
46
What specific condition is gene augmentation therapy often used to treat?
Adenosine de-aminase deficiency (ADA) which is an autosomal recessive disorder.
47
What is the first step of using gene augmentation therapy for the treatment of ADA?
T lymphocytes are removed from the patient and then grown in culture.
48
What is the second step of using gene augmentation therapy for the treatment of ADA, after T lymphocytes have been extracted from the patient and grown in culture?
A retrovirus can the be altered to contain the correct gene for ADA.
49
What is the third step of using gene augmentation therapy for the treatment of ADA, after the retorvirus has been altered?
The virus can then infect the newly grown T cells with the DNA of interest.
50
What is the fourth step of using gene augmentation therapy for the treatment of ADA, after the T cells have been infected with the correct ADA gene??
The cells can be inserted into the patient and the correct gene will be expressed to correct ADA.
51
Is the use of gene augmentation therapy for the treatment of ADA an in vivo or ex vivo technique?
Because this technique is done outside of the patient it is an ex-vivo technique.
52
How is gene replacement therapy carried out?
By using homologous recombination to replace a non-functional gene with a functioning gene.
53
What is the basic idea behind gene replacement therapy?
Inserting normal DNA into cells that contain non-functioning genes.
54
How is the gene of interest inserted into the genome of a cell during gene replacement therapy?
The chromosome containing the non-functioning gene combines with the new DNA during homologous recombination.
55
What happens during gene replacement therapy after the chromosome combines with the new DNA during homologous recombination?
The chromosome will swap the non-functioning gene for functioning genes from the inserted DNA.
56
What must be known before gene replacement therapy can be carried out?
The flanking sequences on the malfunctioning gene, as they must match up with those on the inserted gene.
57
Is gene replacement therapy an in vivo or ex vivo technique?
It is an in-vivo technique as it is performed inside the organism.
58
What does gene inhibition therapy involve?
Silencing a misfunctioning gene by inhibit the translation of its mRNA through the use of an exogenous gene.
59
What creates the misfunctioning genes that can corrected by gene inhibition therapy?
Mutations or the effects of pathogens.
60
What is commonly used to inhibit the translation of mRNAs in gene inhibition therapy?
Antisense RNA’s which will bind the the RNA that is produced by the mis-functioning cell.
61
Is gene inhibition therapy an in vivo or ex vivo technique?
An in vivo technique as it is not performed in the lab.
62
What is gene repair therapy used to do?
To repair abnormal genes.
63
What enzymes can break a DNA strand, leading to the need for gene repair therapy?
Nucleases such as zinc finger nucleases can break a DNA strand meaning that the DNA strand cannot be read as normal.
64
What does gene repair therapy involve?
Inserting DNA that can link the 2 separated strands of DNA together.
This repairs the broken DNA and allows it to function as normal.
65
What will the process of gene alteration therapy affect?
It alters gene regulation which determines whether the gene is turned on or off.
66
What is used to alter gene regulation in gene alteration?
miRNA’s which bind to the RNA’s produced by housekeeping genes.
67
What kind of genes are involved in gene regulation?
Genes that are always turned on and are known as housekeeping genes.
68
How will scientists perform gene alteration if they want a housekeeping gene to produce less proteins?
They can add miRNA’s which bind to RNA produced by the housekeeping and prevent protein synthesis.
69
How will scientists perform gene alteration if they want a housekeeping gene to produce more proteins?
They will introduce miRNA’s that are attached to an inhibitor.
This prevents the miRNA from binding to the mRNA and allows the mRNA to be translated into protein.
70
Gene regulation allows scientists to do what?
To up regulate and down regulate genes at will.
71
What is viral mediated gene transfer also known as?
As transduction.
72
What is viral mediated gene transfer?
The process of using a virus as a vector to insert DNA into a cell.
73
The viruses that are used as vectors for viral mediated gene transfer normally infect what kind of cells?
Mammalian cells.
74
Why do scientists like to use viruses that normally infect mammalian cells as vectors for viral mediated gene transfer?
It makes the process more efficient.
75
What are the 2 modifications that viruses recieve if they are to be used for viral mediated gene transfer?
They are modified to increase their ability to infect a host cell.
They are modified so that they do not cause disease.
76
How are the viruses that are used for each individual patient in viral mediated gene transfer selected?
They are selected based on their ability to recognise and infect certain cells.
Whether the virus infects the cell on a temporary or permanent basis.
77
What determines whether a virus infects a cell on a permanent of temorary basis?
The type of virus that is used to insert the new DNA into the cell.
78
What cells does the herpes virus HSV-1 bind to?
It binds directly to cells of the nervous system.
79
What are the 5 main types of viruses that can be used to for viral mediated gene transfer?
Retroviruses.
Lentiviruses.
Adeno-associated viruses.
Adenoviruses.
Poxviruses.
80
What are the major characteristics of a retrovirus?
Single stranded RNA.
Permanently integrates its genome into a host cell.
81
Why is non-viral mediated gene therapy often preferred to viral mediated gene therapy?
Because of safety concerns about using recombinant viruses for gene therapy.
82
What is a major disadvantage of using non-viral mediated gene therapy over viral mediated gene therapy?
Because they have a lower transfection efficiency.
83
What are the 3 major categories of non-viral mediated gene transfer?
Transfection.
Direct transfer.
Bacterial gene transfer.
84
What is transfection?
It involves the deliberate insertion of genetic material into a eukaryotic cell.
85
What are the 4 major methods of perfroming transfection?
Chemically.
Lipofection.
Electroporation.
Receptor mediated gene transfer.
86
What is the direct transfer method of non-viral mediated gene transfer?
It involves techniques directly transferring DNA into a cell via microinjection or particle bombardment.
87
What is the bacterial mediated gene transfer method of non-viral mediated gene transfer?
It utilises live invasive bacteria such as shigella and salmonella to transfer DNA into a cell via their pilus.
88
What is in-vivo liposome gene delivery?
A method of non-viral mediated gene therapy that uses artificial lipid spheres.
89
How does in-vivo liposome gene delivery work?
The liposomes pass therapeutic DNA through the membrane of a target cell.
90
What are the artificial lipid spheres that are used in in-vivo liposome gene delivery known as?
As liposomes.
91
What do liposomes have inside their aqueous core?
Therapeutic DNA.
92
How are liposomes placed into a tissue?
They are injected or sprayed into the tissue.
93
How does viral receptor mediated gene transfer work?
It uses the viral coat proteins to insert the DNA of interest into a cell.
94
How does viral mediated gene transfer get DNA to enter a cell?
The viral coat proteins bind to specific receptor cells on the cell membrane.
They then insert the DNA of interest into the cell via endocytosis.
95
How is the DNA of interest bought into the cell during viral mediated gene transfer?
Inside a transport vesicle.
Once the vesicle has broken apart, the DNA can be taken to the nucleus.
96
How does the introduction of a 47th chromosome into target cell work?
It revolves around inserting a new chromosome into a target cell.
97
Why is introducing a 47th chromosome into a cell difficult?
Because it is a very large vector that is capable of carrying a huge amount of genetic material.
The immune system can sometimes attack and destroy the artificial chromosome.
98
What dieases is gene therapy used to treat?
Only incurable or life threatening diseases.
99
Why is it important to know which genes are affected by a disease before performing gene therapy?
Because, there is no point in altering the genes of a person if they are not the genes that cause the disease.
100
What must be available for gene therapy to take place?
Copies of the target gene so that they can be used to replace the non-functioning gene.
101
What factor about a gene must be considered before it is used for gene therapy?
Whether the gene can produce enough normal proteins to make a difference.
102
When was the first human gene therapy carried out?
In 1990.
103
Who carried out the first human gene therapy?
A doctor called Ashanti Da Silva.
104
What disease did the first patient to recieve gene therapy have?
Severe Combined Immuno Deficiency (SCID) disease.
105
What causes SCID disease?
A deficiency in the adenosine deaminase (ADA) gene.
106
What was the first step of curing SCID disease in the first case of using gene therapy?
ADA deficient T cells were from the patient and then cells cultured and grown within the lab.
107
What was the second step of curing SCID disease in the first case of using gene therapy, after the T cells had been cultured?
The cells were infected by a modified retrovirus which contained a functioning ADA gene.
The cells were then inserted back into the patient and the disease was cured.
108
How can gene therapy be used to overcome cancer?
By removing blood from a patient and then isolating T cells from the blood.
The T cells are then infected with a modified virus that inserts new genes into the T cells.
The modified cells are then injected back into the patient.
109
Ho do the modified T cells that are used overcome cancer work?
The modified T cells develop receptors that allow for them to target and kill cancer cells.
110
The treatment he treatment of cancer via gene therapy revolves around what 2 techniques?
The artificial and natural killing of cancer cells.
111
What are 3 methods that involve the artificial killing of cancer cells achieved?
By inserting a gene encoding toxin into tumour cells.
By inserting genes that encode for sensitivity to certain drugs into the tumour.
By inserting genes that allow tissues surrounding the cancer tumour to be resistant to chemotherapy.
112
How can gene therapy kill cancer cells naturally?
By inserting genes that stimulate the immune system to kill cancer cells.
113
How can gene therapy be used to cure sickle cell disease?
It revolves around the creation of a therapeutic transgene via RNA interference and the globin gene.
114
What is the first step of using gene therpy to cure sickle cell?
The therapeutic transgene is inserted into a virus.
115
What is the second step of using gene therapy to cure sickle cell, after the transgene has been inserted into a virus?
The virus is used to insert the gene into haematopoietic stem cells.
This leads to the production of a normal beta-globin gene which produces normal haemoglobin.
116
Who is currently trying to cure HIV via gene therapy?
Dr John Rossi.
117
How can gene therapy potentially be used to cure HIV?
By combining anti-HIV drugs with genetically modified stem cells that carry 3 anti-HIV genes.
