6.3 Flashcards
(99 cards)
1
Q
What is Somatic Cell Gene Therapy?
A
Somatic Cell Gene Therapy involves inserting functional alleles into body cells.
2
Q
what is the basic principle of gene therapy
A
the basic principle of gene therapy is to insert a functional allele of a particular gene into cells that contain only mutated and non-functioning alleles of that gene. If the inserted allele is expressed then the individual will produce a functioning protein and no longer have the symptoms associated with the genetic disorder
3
Q
what has knowledge gained from the human genome project allowed for
A
it has led to further possibilities such as using interference RNA to silence genes by blocking translation.
4
Q
when does Cystic Fibrosis occur ?
A
cystic fibrosis occurs when an individual inherits two faulty recessive alleles for a particular gene, as a result the differentiated cells where this gene should be lack the protein product of that gene.
if the functioning alleles for this gene are put back into specific cells so that these cells can make the protein then these cells will function normally
5
Q
Who does Somatic Cell Gene Therapy benefit?
A
Somatic cell gene therapy affects only certain types of cell types.
The alterations made to the patient’s genome are not passed to the patient’s offspring..
6
Q
How can Somatic Cell Gene Therapy treat Cystic Fibrosis?
A
Patients with Cystic Fibrosis lack a functioning CFTR gene.
The alleles can be packaged within a spherical lipid bilayer to make Liposomes.
Liposomes are placed into an aerosol inhaler and sprayed into the noses of patients.
The Liposomes will pass through the plasma membrane of the cells lining the respiratory tract.
If they also pass through the nuclear envelope and insert into the host genome, the host cell will express the CFTR protein - a transmembrane chloride ion channel.
7
Q
why does cystic fibrosis need to be treated regularly with somatic cell gene therapy
A
Epithelial cells lining the respiratory tract are replaced every 10-14 days, so this treatment has to be repeated at regular short intervals.
8
Q
How can Viruses be used in Somatic Cell Gene Therapy?
A
Viruses have been used as vectors.
If a virus that usually infects humans is genetically modified so that it encases the functioning allele to be inserted into the patient, whilst at the same time being made unable to cause a disease, it can enter the recipient cells, taking the allele with it.
9
Q
What are the issues with using Viruses as vectors as gene delivery agents?
A
- Viruses may still promote an immune or inflammatory response
- The patient may become immune to the virus, making subsequent deliveries difficult or impossible
- The Virus may insert the allele into the patient’s genome in a location that disrupts a gene involved in regulating cell division, increasing the risk of cancer
- The Virus may insert the allele into the patient’s genome in a location that disrupts the regulation of the expression of other genes
10
Q
How can Artificial Chromosome be used in Somatic Cell Gene Therapy? (current research)
A
Genes can be inserted into an artificial chromosome that would co-exist with the other 46 chromosomes in the target cells.
11
Q
What is Germ Line Gene Therapy?
A
Germ Line Gene Therapy involves inserting functional alleles into Gametes or Zygotes
12
Q
What are Germ Cells?
A
Reproductive cells that give rise to sperm and ovum
13
Q
Who does Germ line Gene Therapy benefit?
A
The cells of the individual will be altered permanently, so their offspring will also inherit the foreign alleles.
14
Q
What are the issues Germ line Gene Therapy?
A
There are concerns about how the genes potentially being inserted into a location that could potentially disrupt the expression or regulation of other genes or increase the risk of cancer.
Germ line Gene Therapy is considered ethically impermissible for humans.
15
Q
What is Genetic Engineering?
A
Genetic engineering is also known as Recombinant DNA Technology, because it involves combining DNA from different organisms.
It is also called Genetic Modification.
Genes are isolated from one organism and inserted into another organism, using a suitable vector.
16
Q
What is Recombinant DNA?
A
Recombinant DNA is a composite DNA molecule created ‘in vitro’ by joining foreign DNA with a vector molecule such as a plasmid.
17
Q
What are the Four main Stages of Genetic engineering?
A
- The required Gene is Obtained
- A copy of the gene is placed inside a vector.
- The vector carries the gene into a recipient cell
- The recipient expresses the novel gene
18
Q
How can we obtain the required gene using mRNA?
A
mRNA can be obtained from cells where the gene is being expressed.
An enzyme, Reverse Transcriptase can then catalyze the formation of a single stand of complementary DNA (cDNA) using the mRNA as a template.
The addition of primers and DNA polymerase can make this cDNA into a double stranded length of DNA, whose base sequence codes for the original protein.
19
Q
Where are Reverse Transcriptase Enzymes present in Biological Life?
A
Retroviruses, such as HIV, use Reverse Transcriptase enzymes that catalyse the production of cDNA (complementary DNA) using their Viral RNA as a template.
20
Q
How can we obtain the required gene if we know the nucleotide sequence?
A
- The Gene can be synthesised using an Automated Polynucleotide Synthesiser.
- if the sequence of the gene is known, Design Polymerase Chain Reaction (PCR) primers to amplify the gene from the genomic DNA.
21
Q
How can we obtain the required gene using a DNA probe?
A
A DNA probe can be used to locate a gene within the genome and the gene can then be cut out using restriction enzymes.
22
Q
what are restriction enzymes
A
endonuclease enzymes that cleave (split) DNA molecules at specific recognition sites
23
Q
How can we place the gene into a Plasmid vector?
A
Plasmids are obtained from bacteria and mixed with Restriction Enzymes that will cut the plasmid at specific recognition sites.
The cut plasmid has exposed unpaired nucleotide bases, called sticky ends.
If free nucleotide bases, complementary to the sticky ends of the plasmid, are added to the ends of the gene to be inserted, then the gene and cut plasmid should anneal (bind).
DNA ligase enzyme catalyses the annealing.
A gene mu be sealed into an attenuated (weakened) virus that could carry it into a host cell
24
Q
Where else are Ligase Enzymes used in Biology?
A
DNA ligase enzyme is used in molecular biology to join DNA fragments.
It catalyses condensation reactions that join the sugar groups and phosphate groups of the DNA backbone.
These enzymes catalyse such reactions during DNA replication in cells and are also used in the PCR.
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Where are Restriction Enzymes present in Biological Life?
Restriction Enzymes are Endonuclease Enzymes that cleave DNA molecules at specific recognition sites.
Bacteria and Archaea have restriction enzymes to protect them from attack by phage viruses.
These enzymes cut up the foreign viral DNA, by a process called restriction, preventing the viruses from making copies of themselves.
The prokaryotic DNA is protected from the action of these endonucleases.
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How can we place the gene into a Viral vector?
A gene may be sealed into an attenuated (weakened) virus that could carry it into a host cell.
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How can we place the vector in the Recipient Cell?
DNA does not easily cross the recipient cell's plasma membrane.
Various methods can be used to aid the process:
- Heat shock treatment
- Electroporation
- Electrofusion
- Transfection
- Small pieces of Gold or Tungsten are coated with the DNA and shot into the plant cell using a gene gun
- Plasmids are inserted into certain bacterium which naturally inserts its genome into the host cell genomes.
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how does heart shock treatment allow for a vector to be placed into a recipient cell
if bacteria are subjected to periods of hot and cold, and the presence of calcium chloride, their walls and their membranes will become more porous and allow in the recombinant vector. This is because the positive calcium ions surround the negatively charged parts of both the DNA molecules and phospholipids in the cell membrane thus reducing repulsion between the foreign DNA and the host cell membranes
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What is Electroporation?
Electroporation involves using high voltage to disrupt the cell membrane, making it more porous and allowing the introduction of a novel gene into a cell.
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What is Electrofusion?
Electrofusion involves using electrical fields help to introduce DNA into cells.
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What is Transfection?
Transfection involves DNA being packaged into a bacteriophage, which can then transfect the host cell.
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How have Scientists obtained insulin from GM Bacteria?
Scientists can obtain mRNA from beta cells of islets of Langerhans in the human pancreas, where insulin is made.
1. Adding reverse transcriptase enzyme makes a single strand of DNA and treatment with DNA polymerase makes a double strand - the gene.
2. Addition of free unpaired nucleotides at the ends of the DNA produces sticky ends.
3. Now, with the help of ligase enzyme, the insulin gene can be inserted into plasmids extracted from E. coli bacteria. These are now called recombinant plasmids, as they contain inserted DNA.
4. E. coli bacteria are mixed with recombinant plasmids and subjected to heat shock in the presence of calcium chloride ions, so that they will take up the plasmids.
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how do we ensure that transformed (transgenic) bacteria that have resistance to some antibiotics dont escape into the wild
we knock out a gene which means they can not synthesise a particular nutrient
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Genetic Manipulation technology:
what are the advantages and disadvantages of modified microorganisms
+GM microorganisms can make human insulin to treat all diabetics
+human growth hormone can treat people with pituitary dwarfism
-could escape into the wild and transfer marker genes for antibiotic resistance
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Genetic Manipulation technology:
what are the advantages and disadvantages of modified soya beans
+GM soya beans were made resistant to a herbicide so that competing weeds would die and they wouldnt
-gene for herbicide resistance could pass into weeds
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Genetic Manipulation technology:
what are the advantages and disadvantages of modified golden rice
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Genetic Manipulation technology:
what are the advantages and disadvantages of modified pathogens
+ genetically modified viruses can be used to make vaccines as they still have antigens but wont make recipient ill
+modified viruses can also act as vectors in gene therapy
-some problems with use of viruses in gene therapy as the allele may be inserted into the genome in a way that increases the risk of cancer or interferes with gene regulation
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Genetic Manipulation technology:
what are the advantages and disadvantages of modified pharmaceutical proteins
+human pharmaceutical proteins can be inserted into animals and produced in their milk
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What is Electrophoresis?
Electrophoresis is a procedure that separates proteins or DNA fragments according to size or electrical charge.
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what is electrophoresis widely used in
electrophoresis is widely used in gene technology to separate different DNA fragments for identification and analysis
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what is used in electrophoresis
- uses an agrose gel plate covered by a buffer solution
-electrodes are placed at each end of the tank (so electric current can pass through the gel)
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what is the overall charge of DNA?
DNA had an overall negative charge due to the many phosphate groups.
This means it will move to the anode (positive cathode)
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How does Electrophoresis work to separate DNA?
1. The DNA samples are digested with restriction enzymes to cut them, at specific recognition sites, into fragments.
2. While the restriction enzymes are cutting the DNA, the tank is set up.
The Agarose Gel is poured into the central region of the tank. Once the gel is set, buffer solution is added so that the gel is covered and the end sections of the tank contain buffer solution.
3. A loading dye is added to the tubes containing the digested DNA. The digested DNA and the loading dye is added to wells in the electrophoresis gel.
4. Once all the wells have been loaded with the different DNA samples, the electrodes are put into place and connected to a battery.
5. The DNA fragments move through the gel at different speeds. Smaller fragments travel faster, so in a fixed period they travel further.
6. At the end of the period, the buffer solution is poured away and a dye is added to the gel. This dye adheres to the DNA and stains the fragments.
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How does Electrophoresis work to separate Proteins?
The principle for separating proteins is the same as for separating DNA fragments, but is often carried out in the presence of a charged detergent such as sodium dodecyl sulfate (SDS).
This equalizes the surface charge on the molecules and allows the proteins to separate as they move through the gel, according to their molecular mass.
In some cases the proteins can be separated according to mass and then, without SDS, according to their surface charge.
45
what can Electrophoresis of proteins be used for?
what can Electrophoresis of proteins be used for?
This technique can be used to analyse the types of Hemoglobin proteins for the diagnosis of conditions such as:
- Sickle Cell Anaemia
- Aplastic Anaemia, thalassaemia, Leukaemia
46
How is Electrophoresis similar to TLC?
In TLC the molecules pass through a medium and smaller molecules travel faster, therefore further in a fixed time period, than the larger molecules.
47
What is a DNA probe?
A DNA probe is a short (50-80 nucleotides) single-stranded length of DNA that is complimentary to a section of the DNA being investigated.
The probe may be labelled using:
- A Radioactive Marker that can be identified using photographic filmed when it has bound to the piece of DNA.
- A fluorescent marker that emits a colour on exposure to UV light when it has bound to the piece of DNA. Fluorescent markers may also be used in automated DNA sequencing
48
What can DNA probes be used for?
Probes are useful in locating specific DNA sequences:
-To locate a specific gene needed for use in genetic engineering
- To identify the same gene is a variety of different genomes from different species when conducting genome comparisons studies
- To identify the prescence or absence of a specific allele for a particular genetic disease or that gives susceptibility to a particular condition
49
What is a DNA Microarray?
Scientists can place a number of different probes on a fixed surface, known as a DNA microarray.
Applying the DNA under investigation to the surface can reveal the presence of mutated alleles that match the fixed probes, because the sample DNA will anneal to any complementary fixed probes.
The sample DNA must first be broken into smaller fragments, and it may also be amplified using the polymerase chain reaction (PCR).
A DNA microarray can be made with fixed probes, specific for certain sequences found in mutated alleles that cause genetic diseases, in the well.
Reference and test DNA samples are labelled with fluorescent markers. Where a test subject and a reference marker both bind to a particular probe, the scan reveals fluorescence of both colours, indicating the presence of the particular sequence in the test DNA
50
what is PCR
PCR is an artificial method (biomedical technology) that can be used to amplify (increase the amount of) a short length of DNA to millions of copies, enabling it to be analysed
51
what does PCR rely on
It relies on the facts that:
- DNA is made of two antiparallel backbone strands
- Each strand has a 5' and 3' end
- DNA grows only from the 3' end
- Base pairs pair up accordingly to complementary base pairing rules
52
How does PCR differ from DNA replication?
in PCR:
-only short sequences up to 10,000 base pairs of DNA can be replicated, not entire chromosomes
-it requires the addition of a primer molecule to make the process start
-a cycle of heating and cooling is needed to separate the DNA strands, bind primers to the strands and for DNA strands to be replicated
53
What are the steps involved in PCR?
1. Denaturation
2. Annealing
3. Elongation
54
what has sped up the PCR process
Taq polyamerase which is an enzyme obtained from thermothillic bacterium (prevents the DNA from being heated and then cooled to anneal the primers and allow DNA polymerase to work)
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What are DNA Primers and what is the need for them?
Short lengths/fragments of DNA/nucleotides/
single stranded DNA;
DNA polymerase cannot bind to single-stranded DNA
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What is the role of the Magnesium ions?
Cofactors for the enzyme DNA polymerase.
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Outline the steps of PCR
1. The sample of DNA is mixed with DNA nucleotides, primers, magnesium ions and the enzyme Taq DNA polymerase.
2. The mixture is heated to 95 °C to break the hydrogen bonds between complementary nucleotide base pairs and thus denature the double-stranded DNA into two single strands of DNA.
3. The mixture is cooled to 65 °C, so that the primers can anneal (bind by hydrogen bonding) to one end of each single strand of DNA.This gives a small section of double-stranded DNA at the end of each single-stranded molecule.
4. The Taq DNA polymerase enzyme molecules can now bind to the end where there is double-stranded DNA.Taq polymerase is obtained from a bacterium that lives at high temperatures; 72°C is the optimum temperature for this enzyme.
5. The temperature is raised to 72°C,which keeps the DNA as single strands. The Taq DNA polymerase catalyses the addition of DNA nucleotides to the single-stranded DNA molecules, starting at the end with the primer and proceeding in the 5' to 3' direction
6.When the Taq DNA polymerase reaches the other end of the DNA molecule, then a new double strand of DNA has been generated.
The whole process begins again and is repeated for many cycles.
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How does the amount of DNA increase in PCR?
The amount of DNA increases exponentially
(1,2,4,8,16,32,64,128)
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What are the Applications of PCR?
- Tissue typing
- Detection of Oncogenes
- Detecting mutations
- Identifying viral infections
- Monitoring spread of infectious disease
- Forensic science
- Research
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How is PCR used in tissue typing
donor and recipient tissues can be typed prior to transplantation to reduce the risk of rejection
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How is PCR used in detection of oncogenes
if the type of mutation involved in a specific persons cancer is found, then the medication may be better tailored to that patient
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How is PCR used in detecting mutations
a sample of DNA is analysed for the presence of a mutation that leads to a genetic disease. Parents can be tested to see if they have a recessive allele for a particular gene; fetal cells may be obtained from the mothers bloodstream for prenatal genetic screening; during IVF treatment, one cell from an eight cell embryo can be used to analyse the fetal DNA before implantation
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How is PCR used in identifying viral infections
sensitive PCR tests can detect small quantities of viral genome amongst the host cells DNA. this can be used to verify HIV or hepatitis C infections
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How is PCR used in monitoring the spread of infectious disease
the spread of pathogens through a population of wild or domesticated animals or from animals to human populations, can be monitored, and the emergence of new more virulent sub types can be detected
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How is PCR used in forensic science
small quantities of DNA can be amplified for DNA profiling, to identify criminals or to ascertain parentage
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How is PCR used in research
amplifying DNA from extinct ancient sources such as Neanderthal or woolly mammoth bones, for analysis and sequencing. In extant organisms, tissues or cells can be analysed to find out which genes are switched on or off
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what has interference RNA been used to treat
been used to treat cytomegalovirus infections in AIDS patients by blocking replication of the cytomegalovirus
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What are the Similarities and Differences between normal DNA Replication and PCR Replication?
Similarities:
Both processes involve the synthesis of new DNA strands from a template DNA strand.
Both processes require a DNA polymerase enzyme to catalyze the formation of the new DNA strands. However, PCR uses Taq DNA Polymerase which is stable at higher temperatures
Both processes use nucleotides to extend the new DNA strands.
Both processes require a set of primers that anneal to the template DNA strand to initiate DNA synthesis.
Differences:
Normal DNA replication occurs naturally in cells during cell division, while PCR replication is a laboratory technique used to amplify DNA sequences in vitro.
In PCR, heat breaks H bonds between complementary base pairs, whereas, in natural replication - helicase/gyrase enzymes involved in unwinding/unzipping;
Normal DNA replication occurs at physiological temperatures (around 37°C), while PCR replication requires multiple cycles of high-temperature denaturation (around 95°C) and lower-temperature annealing and extension (around 60°C).
Normal DNA replication can amplify entire genomes, while PCR replication is typically used to amplify specific DNA sequences.
Normal DNA replication can introduce mutations In contrast, PCR replication is generally considered to be highly accurate and reproducible.
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what is DNA sequencing
A technique that allows genes to be isolated and read, in order to determine the exact base nucleotide sequence.
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What was the issue with determining Nucleotide Sequence in the 1970s?
Scientists worked from the mRNA transcribed from the gene and not the raw DNA.
RNA is unstable and this process was extremely slow and only suitable for very short genes.
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What was Fred Sanger's DNA sequencing approach?
The Sanger sequencing method involves four key steps:
Each dish contains a solution with the four bases, DNA polymerase and a modified version of one of the DNA bases.
The base was modified in such a way that, once incorporated into the synthesised complementary strand of DNA, no more bases could be added. Each was also labelled with a radioactive isotope.
As the reaction progressed, thousands of DNA fragments of various lengths were made
Gel Electrophoresis the occured. The DNA strands of different lengths are then separated by size using gel electrophoresis, where the DNA fragments migrate through a gel based on their size and charge.
The sequence of the template DNA can be read from the DNA fragments' pattern on the gel, starting from the primer and working towards the end of the template DNA strand.
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How did Sanger obtain a single strand of DNA?
The gene to be sequenced was isolated, using restriction Enzymes.
The DNA was then inserted into a bacterial plasmid (The Vector) and then into an E.coli bacterium host that divided many times, enabling the plasmid with the DNA insert to be copied many times.
These lengths of DNA were isolated using plasmid preparation techniques and were then sequenced.
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what was the negative of sangers DNA sequencing approach
he had to count off the bases one by one, from the bands in the piece of gel- this was very time consuming and thus costly process
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how was the first DNA sequence machine an improvement from sangers method
-fluorescent dyes instead of radioactivity were used to label the terminal bases. These dyes glowed when scanned with a laser beam, and the light signature was identified by a computer.
-this method dispensed the need for technicians to read autoradiograms
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what is a racent fast and cheap method of sequencing genomes
pyrosequencing
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What are the steps involved in Pyrosequencing? (SIMPLE)
1. A long length of DNA to be sequenced is mechanically cut into fragments of 300-800 base pairs, using a Nebuliser.
2. These lengths are then degraded into single-stranded DNA (ssDNA). These are template DNAs and they are immobilised
3. A sequencing primer is added and the DNA is then incubated with the enzymes DNA Polymerase, ATP sulfurylase, luciferase, apyrase and the substrates adenosine 5' phosphosulfate (APS) and luciferin. Only 4 possible activated nucleotides, ATP, TTP, CTP and GDP is added at any one time and light generated is detected
4. One activated nucleotide (a nucleotide with two extra phosphoryl groups) such as TTP is incorporated into a complimentary strand of DNA using the strand to be sequenced as a template. As this happens, two extra phosphoryls are released as pyrophosphate (PPi). In the presence of APS, the enzyme luciferase converts luciferin to oxyluciferin. This converts general visible light which can be detected by a camera. The amount of light generated is proportional to the amount of ATP that is available and thus indicated how many of the same type of activated nucleotide were incorporated adjacently into the complimentary DNA strand.
Unincorporated activated nucleotides are degraded by apyrase while the reaction starts again with another nucleotide.
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What are the Activated Nucleotides used?
Pyrosequencing uses four types of nucleotides:
Adenosine triphosphate (ATP)
Cytosine triphosphate (CTP)
Guanine triphosphate (GTP)
Thymine triphosphate (TTP).
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What is the difference between an Nucleoside and Nucleotide?
The main difference lies in their molecular composition as Nucleosides contain only sugar and a base whereas Nucleotides contain sugar, base and a phosphate group as well.
A nucleotide is what occurs before RNA and DNA, while the nucleoside occurs before the nucleotide itself.
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What is Bioinformatics?
A method that uses very large national and international databases to access and work with DNA sequence information.
It would have been impossible to store and analyse these data prior to computers and microchips.
Software packages are specially designed for this purpose.
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What are the Applications of Gene Sequencing?
- The Human Genome Project
- Genome-wide comparisons between individuals and species
- Determining Evolutionary Relationships
- variations between individuals
- Predicting the amino acid sequences of proteins
- Synthetic Biology
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What is the Human Genome Project?
Scientists in different countries collaborated to decode the human genome. This is the order of bases on all the human chromosomes.
It was discovered the human genome contained only about 24,000 genes.
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What is the importance of the Human Genome Project?
1. **Understanding human biology**: By mapping the human genome, researchers gained a much better understanding of how human cells and organs function, which has led to advances in medicine and biotechnology.
2. Disease diagnosis and treatment: The HGP has enabled scientists to identify the genetic basis of many diseases, which has improved diagnosis and treatment options for patients.
3. Drug development: The HGP has facilitated the discovery and development of new drugs by identifying specific genes and proteins that play a role in disease.
4. Forensic science: The HGP has improved the accuracy of DNA profiling, which has made forensic investigations more reliable.
5. Evolutionary biology: The HGP has shed light on human evolution and the relationships between different species, as well as the evolutionary history of our own species.
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how has gene sequencing shown comparisons between species
-some genes are unique to certain species
-most of our genes have counterparts in other organisms
-genes that work well tend to be conserved by evolution (pigs and humans have simmilar genes for insulin)
-many of the differences between organisms is because some shared genes have been altered and work in a subtly different way. Some changes to regulatory regions of DNA that do not code for proteins have also altered the expression of the genomes
84
how has gene sequencing shown evolutionary relationships
comparing genomes of organisms thought to be closely related has helped confirm evolutionary relationships and has led to knowledge on the relationships- some organisms may be reclassified.
The dna from bones and teeth of some extinct animals can be amplified and sequenced so that the animals evolutionary history can be verified
85
how has gene sequencing shown variation between individuals
0.1% of our DNA is not shared with others
DNA sequences can differ due to random mutations such as substitution.
The places on the DNA where these substitutions occur are called single nucleotide polymorphisms or SNPs. Some have no effect on the protein, some can alter a protein or alter the way a piece of RNA regulates the expression of another gene
Methylation of certain chemical groups in DNA plays a major role in regulating gene expression in eukaryotic cells. Methods to map this methylation of whole human genomes can help researchers understand the development of certain diseases (epigenetics)
86
how has gene sequencing helped in predicting the amino acid sequence of a protein
If we have the organism genome sequence and know which gene codes for a specific proteins by using knowledge of which base triplets code for which amino acids, they can determine the primary structure of proteins.
The researcher needs to know which part of the gene codes for exons and which codes for introns.
87
What is Synthetic Biology?
Synthetic Biology is concerned with designing and building useful biological devices and systems.
It encompasses biotechnology, evolutionary biology, molecular biology, systems biology and biophysics.
The sequences of DNA found by analysing genomes provide potential building blocks for synthetic biologists to build devices
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What can Synthetic Biology be used for?
- Information storage on DNA
- Production of medicines
- Novel Proteins
- Biosensors
- Nanotechnology
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what are bioethics
Synthetic biology raises issues of ethics and biosecurity.
There are many advisory panels and many scientific papers on how to manage rewards and potential for new systems with associated risks.
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What is DNA Profiling?
DNA profiling, also known as DNA fingerprinting or genetic fingerprinting, is a technique used to identify and compare individuals based on their DNA sequences.
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what are tandem repeats
tandem repeats are repetitive segments of DNA that do not code for proteins. They all feature the same core sequence
some types are highly variable and are called variable number tandem repeats (VNTRs)
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what are the steps for DNA profiling
1. DNA is obtained from the individual.
2. The DNA is then digested and cut into fragments with restriction enzymes which will cut the DNA at specific recognition sites.
3. The fragments are separated by Gel electrophoresis and stained. Larger fragments travel the shortest distance in the gel.
4. A banding pattern can be seen.
5. The DNA to which the individual is being compared to is treated to the same steps.
6. The branding patterns of DNA can then be compared.
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What type of DNA is analysed in DNA profiling?
Short tandem repeat (STR) sequences of DNA are used.
These are highly variable short repeating lengths of DNA which can be separated by electrophoresis.
The exact number will vary person to person.
each STR is polymorphic but the number of alleles in the gene pool for each one is small. Thirteen STRs are analysed simultaneously. There is a low chance of two people sharing STR sequences apart from twins
This technique is highly sensitive and even trace DNA can produce a result. Old DNA can also be used to assess new evidence
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What are the Applications of DNA profiling?
Forensic science - brings about convictions, establishes the innocent and people previously wrongly convicted.
Maternity and paternity disputes - comparing DNA profiles of mother, father and child can establish maternity and/or paternity. (half of STR fragments from father...)
Analysis of disease - protein electrophoresis can detect the type of proteins specific to certain diseases.- can aid diagnosis of sickle cell anaemia or repeat sequences for huntingtins
