Gene Expresssion Flashcards
(135 cards)
1
Q
Define frame shift with regard to genetic mutations
A
Frameshift- addition of one base or deletion of one base which causes all bases to shift changing all the codons
This can cause impacts to many amino acids likely producing proteins that cannot function properly
2
Q
Describe the different gene mutations that can occur
A
- Addition
Insertion of 1 or more nucleotides - Deletion
Removal of 1 or more nucleotides - Substitution
1 or more nucleotides replaced with another - Inversion
A cut portion of a gene is inverted 180oc then rejoined in the same place - Duplication
A whole gene or section of a gene is duplicated so that 2 copies appear on the same chromosome - Translocation
A section of a gene is attached to a separate gene
3
Q
Name and describe the 3 forms of substitution mutation
A
Silent mutation - the mutation doesn’t alter the amino acids likely producing sequence (DNA = Degenerate)
Missence - the mutation alters a single amino acidd in the polypeptide chain
Nonsense - the mutation create a premature stop codon preventing the rest of the chain from undergoing translation
4
Q
Mutations occur spontaneously, what does that mean
A
Mutations occur continuously and spontaneously without exposure to mutagenic agents
5
Q
Def of stem cell
A
Self-renewing undifferentiated cell that has the ability to differentiate into any other specialised cell
6
Q
Explain the ability of stem cells
A
All genes present in the cell can be transcribed therefore it has the potential to synthesise all proteins
7
Q
What are the 3 groups of stem cells
+ explain them
A
- Totipotent
- divide to produce any cell type including trophoblast - Pluripotent
- all cell types of an organism (not trophoblast) - multipotent
- limited number of cell types
8
Q
What can totipotent cells divide to produce
A
Any type of body cells
9
Q
What happens to totipotent cells during development
A
During development, totipotent cells translate only part of their DNA, resulting in cell specialisation
10
Q
Where are the 3 types of stem cells found
A
Pluripotent
- found in embryos
Multipotent
- mature mammals
Unipotent
- mature mammals
11
Q
all conditions being treated with stem cells, involve transplants of bone marrow tissue from a donor to a patient.
Explain why this is an effective therapy for many disorders of the blood or immune system?
A
Disorder of the blood or immune system arise due to faulty blood cells
Donor bone marrow contains stem cells that will produce healthy blood cells
The patients own bone cells are destroyed with chemotherapy
12
Q
How do we obtain embryonic stem cells
A
- Embryo allowed to develop at blastocyst stage
- Inner cell mass cells are harvested
(consisting of undifferentiated and pluripotent cells)
13
Q
Explain the ethnical and medical concerns of use of embryonic stem cells
A
Ethical
- involved destruction of human embryo
Medical
- antigens on embryonic cells would be recognised as foreign by patient therefore immunosuppressants would need to be taken
- ability of stem cells to continuously divide may lead to tumours developing
14
Q
Sources and type of fetal stem cells
A
Sourced from abortion & miscarriage
They are multipotent stem cells
15
Q
Sources and type of unbiblical cord stem cells
A
Sources - umbilical cord/ umbilical cord blood
(This means no ethical issues)
Contains multipotent and haematopoietic (blood) stem cells
16
Q
Sources and type of adult stem cells
A
Sources
- bone marrow transplants
(Most accessible stem cells)
Multipotent stem cells
17
Q
What are the advantages and issues of using induced pleuripotent stem cells
A
Advantages
- can use patient’s own multipotent stem cells so will not be rejected
(No need for immunosuppressant)
Issues
- stem cells can continue to divide continuously possibly leading to tumours or cancer developing
18
Q
Def of promoter region
A
Region of gene where transcription factors & RNA polymerase bind
19
Q
Def of transcription factors
A
Transcription factors
- proteins that bind o DNA & help RNA polymerase bind to the promoter controlling gene expression by either stimulating or inhibiting transcription of target gene
20
Q
Def of RNA polymerase
A
RNA polymerase
- synthesis mRNA (catalyses formation of phosphodiester bonds between RNA nucleotides
21
Q
If a transcription factor activates transcription what does it do
A
They may help the general transcription factors and/or RNA polymerase bind to the promotor region increasing transcription of the gene
22
Q
Transcription factors can be activators and repressors
True or false
A
True
Some transcription factors activate transcription
Other transcription factors repress transcription
23
Q
If a transcription factor represses transcription what does it do
A
This repression can work in a variety of ways
- repressor may get in the way of the basal transcription factors
- get in the way of RNA polymerase
- preventing binding of RNA polymerase to the promotor region so stop transcription starting
24
Q
What is combinatorial regulation in terms of gene expression
A
Combinatorial regulation is when
Many genes are controlled by several different transcription factors, with a specific combination needed to turn the gene on
25
What is oestrogen and what does it work to control
- oestrogen is a steroid hormone
- it is small, lipid based so diffuses across the membrane and passes into nuclear pores
- oestrogen is involved in female fertility cycle and also responsible for sperm production
26
Outline the oestrogen stimulation pathway
1) oestrogen diffuses across membrane into cytoplasm
2) oestrogen diffuses through nuclear pores into nucleus
3) within nucleus, oestrogen attaches to ERalpha oestrogen receptors held in protein complex, this causes the ER alpha oestrogen receptors to undergo a conformational change
4) new shape of the ER alpha oestrogen receptors help allows it to detach from protein complex and diffuse towards the gene to the expressed
5) the ER alpha oestrogen receptor binds to a cofactor which enables it to bind to the promoter region of the gene, this stimulates RNA polymerase binding and gene transcription
27
Where does oestrogen act to stimulate gene expression
Oestrogen works in the nucleus by binding to ER alpha receptors held within protein complex
28
What happens to the ER alpha receptor when oestrogen binds
When oestrogen binds the receptor undergoes a conformational change the new shape allows it to detach from the protein complex and diffuse towards target gene
29
At the target gene what does oestrogen receptor allow
The ER alpha oestrogen receptor bound to promoter region stimulates RNA polymerase to bind and gene transcription to occur
30
What does alternative or differential splicing mean for the final amino acid sequence
Alternate or differential splicing (regulated in eukaryotes) allows single gene to code for several proteins
31
What happens in alternative or differential splicing
In alternative or differential splicing
Single gene codes for several proteins
By either including or excluding particular exons from the final mRNA
The proteins translated from alternativesly spliced mRNA will contain differences in their amino acid sequence
32
How does alternative splicing affect biodiversity
Alternative splicing greatly increases the biodiversity of proteins that can be encoded by the genome;
33
What does small interfering RNA do in gene expression
- inhibits translation of mRNA produced from target gene
- small double-stranded RNA molecules called siRNA bind to mRNA that has been transcribed from target genes because their bases are complementary
- each siRNA attached to protein complex which is able to break down the mRNA that have been transcribed from target genes
Therefore the mRNA is unable to translated into polypeptide chain
34
What is the role of tumour suppressor genes
Found in all cells
These genes inhibit cell division to regulate rate of cell division
35
What causes tumour suppressor genes to not function
Increased methylation of tumour suppressor genes inhibits this tumour suppressant gene
36
What happens when tumour suppressor genes is not expressed
When tumour suppressor genes not expressed, cell division not inhibited so cell divides uncontrollably
… tumours and cancers form
37
What is an oncogene
Mutated gene from proto-oncogene which stimulate cell division
38
How do oncogenes cause cancer
Oncogenes capable transforming cells into cancerous cells because they cause excessive cell division
39
How does methylation effect proto-oncogene
Decreased methylation of proto-oncogene causes gene to be over-expressed
Over expression stimulates cell division
40
What is oestrogen
Oestrogen is a hormone that can bind to receptors on transcription factors to increases expression of genes
41
Environmental and genetic factors that affect cancer
Environmental:
Exposure to radiation
Smoking
Poor diet
Alcohol consumption
Genetic:
Having certain alleles (BRCA 1 allele increase breast cancer risk)
42
Explain why not all cells are affected by oestrogen
Not all cells have the ER alpha oestrogen receptors
43
44
In RNA interference pathway how is siRNA formed
Double stranded RNA produced by RNA dependent RNA polymerase is hydrolysed into smaller fragments called siRNA
45
Wha happens to siRNA to allow it to bind to mRNA
In cytoplasm siRNA binds to protein complex using energy from ATP to separate siRNA stands exposing nucleotide bases that an bind to mRNA
46
What happens when siRNA binds to mRNA
The mRNA molecule is cut into fragments by protein complex/enzyme associated with the siRNA. Cutting the mRNA prevents in being translated so no protein produced
47
Therapeutic application of siRNA
SiRNA created against Viral genetic material
- will signal for their degrading and stop virus from replicating inside host
SiRNA used as cancer treatment
- target oncogenes that have been expressed
48
Define epigenetics
Epigenetics refers to heritable changes in gene function, without changes to the base sequence of DNA
49
What does it mean in DNA is condensed or less condensed
Condensed DNA: more tightly packed genes cannot be transcribed ( *epigenetic silencing* )
- inhibition promoter region and gene is hidden
Less condensed DNA: active genes are wrapped so that the DNA is exposed and can be transcribed
- activation promoter region and gene is exposed
50
What covers histone proteins and changes the shape of DNA
The DNA and histones are covered in chemical (called Tags)
This layer of chemicals determines the shape of DNA histone complex (either condensed or less condensed)
51
Def of epigenome
All of the chemical modifications to all histone proteins and DNA ( except base changes) in an organism
*not fixed, like the DNA code, it can change*
52
Examples of environmental factors that chemical tags respond to
- smoking, stress, exercise, diet
These can cause epigenetic changes
Internal signalling from the body’s own cells can also cause modifications to occur
53
Explain how epigenetic changes can cuase identical twins to become more distinguishable as they age
Despite having same DNA, their epigenomes change independently, leading to differences. Changes to the epigenome are caused by changes in environmental factors.
54
How does acetlyation and methylation affect the DNA histone complexes to become more condense
DNA histone complex can become condensed by:
Decreased acetylation of histones
- inhibits transcription/expression
Increased methylation of DNA
- inhibits transcription
55
How does acetlyation and methylation affect the DNA histone complexes to become less condense
DNA histone complex can become less condensed by:
Increasing acetylation of histones
- increases transcription/expression
Decreased methylation of DNA
- increases transcription
56
What does the process of acetylation of DNA entail
Histone proteins being chemically modified by addition of acetyl group to the amino acid lysine
(
57
What does the process of methylation of DNA entail
DNA chemically modified through the addition of methyl group (to base cytosine) without changing the base sequence
58
Def of cancer
Uncontrolled division of cells/mitosis to produce a tumour
59
Types of mutagens that can increases chances of cancer
Exposure to ionising radiation (UV light, X-Rays, Gamma rays)
Carcinogenic chemicals (benzene, smoking)
Genetic predisposition
Low fibre/high fat diets
60
What happens when most cells mutate
They are destroyed by early cell death ( apoptosis) or immune system preventing them forming cancer tumours
61
What do normal proto-oncogenes do
Porto-oncogenes stimulate cell division
62
If proto-oncogene mutate then what happens to cells
If proto-oncogenes mutated then oncogenes produced
Oncogenes = activation and expression
Produces cancerous cells due to excessive cell division
Decreased methylation of proto-oncogenes causes them to be overexpressed = stimulating more cell division possibly leading to cancerous tumour
63
What do normal tumour suppressor genes do
Inhibit cell division controlling cell cycle
64
What happens to mutated tumour suppressor genes and why do they cause cancer
Increased methylation of Tumour suppressor genes inhibit gene expression so division is not inhibited causing cells to divide uncontrollably
65
Def of metastasis
Process of tumour cells developing into secondary tumours in other organs
66
Stages of carcinogenesis (+what happens in each stage)
1. Cells divide uncontrollably
- form tumour
2. Metastasis
- tumour cells develop into secondary tumours in other organs
3. Damage
- enzymes released by the cancer cells enabling them to digest a path through new tissue
4. Tumour increases in size
- tumour secretes growth factors that make new blood vessels grow supplying blood and nutrients
5. All tumours may cause harm
67
How can cancerous tumours cause harm
1. Damaging the organ in which the tumour is located
2, causing blockage or obstruction
3. Damaging other organs by exerting pressure
68
*describe the function of proto-oncogenes and indicate how they relate to cancer*
Proto-oncogenes are genes that code for proteins that regulate cell growth (growth factors) and cell differentiation.
Proto-oncogenes can mutate to become oncogenes that prevent control of cell growth leading to cancer
69
How do proto-oncogenes normally stimulate cells to divide
Growth factors attach to a protein on cell surface membrane. Genes are activated that causes DNA to replicate and cell to divide
70
How do oncogenes cause cancer
Oncogenes are mutated genes that can case cancer through deregulation of cell division as division is constantly activated.
They can do this by:
Receptor proteins on the cell surface membrane can be permanently activated - cell division switched on even in absence of growth factor
Oncogenes may code for growth factors that is produced in excess
Hypomethylation of oncogenes = activation so incr growth = tumour
71
Describe the function of tumour suppressor genes and indicate how they relate to cancer
(Opposite role of Proto-oncogenes)
Slow down cell division, repaire mistakes and induces cells death (apoptosis)
Therefore mutations in this gene result in uncontrolled cells division
72
How do tumour suppressor genes normally control cell division
Tumour suppressor genes are normal genes that code for proteins that regulate cell cycle
The proteins coded by this gene carry out:
- DNA repair
- Slowing cell cycle by ensuring checks are made
- signalling apoptosis (cell death) when faulty
73
How does oestrogen cause a tumour to develop
Oestrogen can promote transcription in a cell by the oestrogen stimulation pathway
74
Genes may be controlled by oestrogen in different ways
If the gene controls cell division and growth, it will be activated by oestrogen and this contributed division could form tumour
75
How do mutated tumour suppressor genes cause cancer
Hypermethylation of DNA causes transcription-inhibiting proteins to bind to DNA, if this occurs around tumour suppressor genes this could result in tumour development ad the necessary regulatory proteins coded for by tumour suppressor genes not produced (gene silenced)
RNA interference by siRNA targeting tumour suppressor genes for breakdown can also lead to tumour development for the same reason
76
How are iPS cells produced
Somatic cells (specialised) converted into iPS cells by activating genes using protein transcription factors
77
After menopause, risk of breast cancer increases why?
After menopause the ovaries diminishes, however the fat cells of the breasts produces more oestrogen.
Oestrogen in breasts may trigger breast cancer in post-menopausal women.
Tumour development is increased by:
- Tumour cells also producing oestrogen
- WBC are also drawn to tumour & ^ oestrogen production
78
How does oestrogen cause a tumour to develop
Oestrogen can promote transcription in a cell by the oestrogen stimulation pathway
79
Compare benign and malignant tumours
B & M- can grow to large size
B- grow slowly
M- grow rapidly
B- cells nucleus has normal appearance
M- cell nucleus larger and darker du to abundance of DNA
B- of tern well differentiated (specialised cells)
M- cells become de-differentiated (unspecialised)
B- cells produce adhesion molecules that make them stick together so remain within tissue
M- cells do not produce adhesion molecules and so tend to spread around the body (metastasis)
B- tumours surrounded by a capsule of dense tissue so remain compact structure
M-tumours not surrounded by capsule can grow finger like projections
B- much less likely to be life threatening but can disturb function of organs
M- more likely to bee life threatening as abnormal tissue replaces normal tissue
B- tend to have localised effect on body
M- tend to have systemic (whole body) effects
B- can usually be removed by surgery alone
M- removal usually involves radiotherapy and chemotherapy as well as surgery
B- rarely reoccur after treatment
M- more frequently reoccur after treatment
80
How are epigenetic changes effect passed on to offspring
Epigenetic markers can be inherited by offspring this means an individual can influence gene expression of offspring
81
How does peptide hormone change gene expression
Peptide hormones bind to cell surface membrane & trigger a secondary messenger response.
Secondary messenger response leads to activation or inhabitation of transiprciton
82
Factors that can affect cancer
Environmental factors
- exposure to radiation
- smoking
- alcoholic consumption
- eating diet high in fat
Genetic factors
- BRCA1 allele increases chance of developing breast cancer
83
How does epigenomic changes affect transcription and why?
Epigenome interactions with chromatins and changes structure causes chromatin to become either
- more condense preventing transcription factors from binding so transcription is inhibited
- less condense so easier access to transcription factors promoting transcription
84
What are epigenetic markers
Epigenetic markers are groups that don’t alter base sequence but influence chromatin structure therefore affecting transcription
85
How can research prevent cancers (gene wise)
Understanding what increases the change of mutations in oncogenes & tumour suppressor genes can help prevent cancer.
These preventative measures will decrease risk of developing cancer
E.g BRCA1 mutation increases risk of developing breast cancer if mutation is incentivised preventative surgery can be used
86
87
Describe the roles of two named types of enzymes used to insert DNA fragments into plasmids
Type: Restriction (endonucleases)
Role: cut DNA at specific nucleotide sequences to leave sticky ends
Type: Ligase
Role: join DNA strand together
88
Name techniques that scientists have used when analysing viral DNA to determine that the viruses were closely related
- PCR
- DNA fingerprinting
- Gel electrophoresis
- DNA sequencing
89
Why is understanding of the genome important in the development of vaccines
Determining the genome allows the sequence of proteins that derive from the genetic code to be determined and therefore may identify the structure of antigens for use in vaccine development
90
Why are complex organisms like humans complicated as their genome is not always the protome
These complex organisms contains
- large amounts of non coding DNA which can be hard to identify from the coding
- also presence of regulatory genes
- process of alternative splicing in also effect gene expression and proteins production
91
Def of recombinant DNA (rDNA)
Sequence of altered DNA with the introduction of nucleotides from a different source
92
Def of transgenic organism
An organism that constrains nucleotide sequences from a different species
93
Why can addition of a different sources DNA allow for the production of different proteins
The mechanisms of transcription and translation are also universal which means that the transferred DNA can be translated and expressed within the genetically modified organism
94
Def of genetic engineering
Changing an organism’s genes (usually adding a gene from a different species)
95
Process of genetic engineering
1) identification of the desired gene
2) isolation of desired gene
3) multiplication of the desired gene
4) transfer of the desired gene by vector
5) cells with desired gene are identified by a marker and cloned
96
Process of genetically engineering bacteria to produce human insulin
1) human insulin gene cut out of DNA by restriction enzyme
2) human insulin gene inserted into plasmid of bacteria by DNA ligase enzyme
3) Plasmid acts as a vector carrying the gene to bacteria cells
(Bacteria cells now transformed)
4) human insulin gene causes bacterial cell to make human insulin proteins
97
Def of Restriction enzyme
Enzyme that Cuts DNA at a specific sequence
- can be used to cut out a gene from a chromosome
- also cut open plasmid to allow a gene to be inserted
98
Def of DNA ligase
Enzyme that joins together the DNA of the gene and plasmid which is now called the recombinant plasmid
99
Def of transformation
Introducing the DNA into a bacterial cell
100
While making recombinant DNA using restriction endonuclease enzymes
What can be formed?
Sticky ends can form
These are small tails of unpaired bases on each end on the desired DNA stand produced
101
Outline the role of sticky ends in producing recombinant DNA
Sticky ends can make it dairy to bind (anneal) DNA fragments to another organism’s DNA
as they can easily from hydrogen bonds with complementary base sequence
102
Why is it important that they both vector’s DNA and target DNA are cut with the same restriction enzymes
103
What are the different ways in which recombinant DNA can be produced
1) using reverse transcriptase
- mRNA isolated and then reverse transcriptase and free nucleotides used to make cDNA
2) using restriction endonuclease enzymes
- palindromic sequence of DNA cut with restriction endonuclease enzymes leaving fragment with sticky ends
3) using gene machine
- data base used to produce DNA fragment which is then made by computer
104
How can recombinant DNA be produced using a gene machine
1) database used to produce desired DNA fragment
2) first nucleotide in the sequence is fixed to a support
3) nucleotides added step by step in correct order, with protecting group
4) short section of DNA is called oligonuleotides and these are joined together to make longer DNA fragment
105
What is an oligonucleotide
Short section of DNA rough 20 nucleotides long which are produced making recombinant DNA in gene machine
106
What are marker genes
Marker genes are genes inserted into recombinant DNA so that we can identify the successfully transformed bacteria
(Markers are often either antibiotic resistance or fluorescence)
107
Stages of genetic engineering with adding foreign gene into plant cell by bacteria vector
1) foreign gene + antibiotic resistance gene inserted into Ti plasmid
2) bacteria grown in agar with antibiotic and transgenic bacteria isolated
3) plant infected with transgenic bacteria
3) transformation occurs as transgene is incorporated into plant’s DNA
108
Benefits of genetic engineering in agriculture
- can be used to increase the nutritional content of food
e.g lowering vitamin A deficiency so decreases eye problems
- can lower the cost for farmers
E.g
- can increases yield for farmers
E.g crops will mature faster and there is an increased tolerance to salt/drought/temperatures
109
Issues with genetic engineering in agriculture
- may be contamination of nearby non-GM crops creating weed resistance to herbicides
- insects/bacteria could also develop resistance to pesticides making them harder to kill
- long term effects on human health unknown
- reduces biodiversity meaning species more at risk of dying from the same disease
- consumers may not know they are eating GM foods
- ethical concerns with GM animals to exhibit certain characteristic
110
Process of using reverse transcriptase to produce fragments of DNA
1) isolate mRNA from a cell expressing the gene
2)the mRNA used as a template and DNA nucleotides and reverse transcriptase added to make DNA
3) A single stranded cDNA (complementary DNA) synthesised with addition of DNA polymerase enzyme
4) DNA polymerase coverts the cDNA stand into double stranded DNA molecule
111
Advantages and disadvantages of using reverse transcriptase to make fragment of DNA
Advans
- easier for scientists to find the gene because specialised cells will make specific types of mRA
- mRNA doesn’t contain intron regions so only the gene is being made
- large amounts of mRNA in cell
Disadvantages
- more steps involved
-time consuming
-requires more technical expertise
112
Advans and disadvans of using restriction enzymes to make fragment of DNA
Advans
- sticky staggered ends on DNA fragments makes DNA ligation and recombinant DNA production easier
Disadvans
- contains intron regions
113
Advans and disadvans of using gene machine to make fragment of DNA
Advans
- extract DNA fragment can be designed with custom sequence
- fragment can be designed to contain markers and sticky ends
Disadvans
- requires the amino acid sequence of the desired protein
114
What are the types of methods of DNA amplification
1) in vitro gene cloning - using PCR outside living organism
2) in vivo gene cloning - inside living organism using bacteria
115
What is needed to amplify a gene using PCR
1) Free DNA nucleotides - join together to form the new DNA strand
2) DNA polymerase enzyme- enzyme that condenses together nucleotides to from new DNA stand
3) DNA or mRNA of gene - acts as a template to align nucleotides in correct order according to complementary base pairing
4) primer - an artificially made small single stranded sequence that is complementary to gene which allows DNA polymerase to join nucleotides together
116
What is the process of DNA amplification using PCR
Include temps
1) mixture of DNA sample. Primers, DNA polymerase enzyme
2) DNA mixture then heated to 95oc to break H bonds between strands
3) mixture then cooled to between 50-60oc so that primers can bind (anneal) to the now exposed bases on DNA stands
4) reaction mixture is heated to 72oc so DNA polymerase lines up free DNA nucleotides alongside each template strand and join them together
5) two new copies of the fragments of DNA are formed in 1 PCR cycle
So cycle is repeated many times
117
Process of in vivo cloning to amplify DNA
1) DNA fragments is inserted into the vector’s DNA
(Either bacteria = plasmid or bacteriophages = virus)
2) vector DNA isolated and then restriction endonuleases and DNA ligase used to stick fragments and vector together in process called **ligation**
3) new combination of bases in DNA called recombinant DNA
4) vector DNA with recombinant DNA then added to host cell causing cell to become transformed
5) these cells then grown on agar plates to develop colonies
6) marker genes used to identify transformed cells allowing them to be isolated
7) transformed cells allowed to grow further
118
The advantages of genetic engineering organisms to produce recombinant human proteins
-more cost-effective to produce in large volumes
- simpler
- faster to produce many proteins
- reliable supply available
- proteins are engineered to be identical to human proteins
119
Def of gene therapy
Using various mechanisms to alter a persons genetic material to treat or cure a disease
120
What is a DNA probe
Short, single-stranded piece of DNA that are labelled radioactively or fluorescently so that they can be identified
121
What types of DNA probes are most commonly used
- radioactively labelled probes which are made up of nucleotides with the isotope 32P
- fluorescently labelled probes which emit light under UV light
122
Advantages of in vitro gene cloning
- extremely rapid
- it does not requires living cells. All that is required is a base sequence of DNA
123
Advantages of in vivo gene cloning
- it is particularly useful where we wish to introduce a gene into another organism
- it involves almost no risk of contamination as gene has been cut by same restriction endonuclease
- it is very accurate
- it cuts out specific genes therefore a very precise procedure
- it produces transformed bacteria that can be used to produce large quantities of gene prodcuts
124
What must DNA probes be structure wise
- complementary to the desired gene
- single stranded (so can bind to inzipped gene)
- contained labelled nucleotides so it can be visualised
125
What is DNA hybridisation
Section of DNA or RNA is combined with a single stranded section of DNA which has complementary bases.
126
What are VNTRs in genetic fingerprinting
VNTR - variable number tandem repeats
Are regions of bases found in the non-coding part of DNA
127
What is true about VNTR between people which means that w can use it to identify DNA
The lengths of VNTRs varies between different people, which means that they can be used to identify the source of DNA from tissue samples
however more closely related individual will have more similar VNTRs as they are inherited
128
What is gel electrophoresis
Process used to separate DNA fragments according to their size
129
Process of gel electrophoresis
1) DNA fragments placed on agar gel and voltage applied across it
2) resistance of the gel is higher with larger fragments, they move slower
3) over a fixed period of time, smaller fragments move further and the DNA fragments can be identified
4) if DNA fragment was labelled then
- radioactive DNA probes determined by placing sheet of X-Ray film over agar gel then allowing it to develop to show fragments positions
- if fluorescent prose then uv light passed over the gel to show the fragments
130
Which way does DNA fragments move in gel electrophoresis and why
DNA moves from the negative end to the positive end
this is because DNA has a negative charge
131
Process to locate a specific allele of genes using DNA probes and DNA hybridisation
1) select gene being located
2) produce a fragment of DNA with complementary base sequence to the located gene
3) amplify this fragment using PCR and add a marker to make DNA probes
4) test sample DNA by immobilising the DNA on a nitrocellulose filter
5 separate the strands
6) add the DNA prove and allow it to hybridise with the gene
7) wash off the unhybridised probes
8) remaining hybridised DNA can be labelled using wither Fluorescence or X-ray film depending on probe used
132
Uses of genetic screenings like DNA hybridisation to identify disease causing genes
- determine the probability for Couple having offspring with genetic disorder
- detercting oncogenes which are responsible for cancer
- making personalised medicine based on genotype which can increase effectiveness of treatment
133
How can genetic screening for diseases be used in genetic counselling
- genetic counsellors can make couples aware of the chances of their children being affected by diseases
- inform couple on the effects of inherited diseases , emotionally, psychologically, medical and socially
- make couples aware of other medical tests that can help prevent children having condition e.g screening in IVF
- counsellors discuss with the patient the best course of treatment and thier prospects of survival after screening for mutations or disease causing genes
134
135
Use of DNA probe screening in medicine
- used to help identify inherited conditions
- used to help determine how a patient will repose to specific drug
- usss to help identify health risk
