manipulating Genomes

Question 1

Describe Early DNA research

Answer 1

• by 1970s the structure of the DNA was known as were the sequences of base triplets that coded from the various amino acids
• at this time it was difficult to work out the sequence of the nucleotide base triplets in genes
• in 1969 a gene was isolated from a bacterial chromosome
• in 1972 a belgian biologists sequenced a gene that codes for the protein coat of a virus, MS2 both scientists worked from the mRNA transcribed from the gene and not the raw DNA
• RNA is unstable and this whole process was extremely slow and only suitable for very short genes
• 1975 the British biochemist Fred Sanger developed a method that ultimately allowed scientists to sequence whole genomes

Question 2

Describe Fred Sanger’s DNA sequencing approach

Answer 2

• approach was to use a single strand of DNA as a template for four experiments in separate dishes
• each dish contained a solution with 4 bases - A,T,C and G plus an enzyme DNA polymerase
• to each dish a modified version of one DNA base was added - this was modified in such a way that once incorporated into the synthesised complementary strand of DNA no more bases could be added and each modified base was also labelled with a radioactive isotope
• as the reaction progressed thousands of DNA fragments of varying lengths were generated
• DNA fragments were passed though a gel by electrophorsis
• smaller fragments travelled further so the fragments travelled by length
• the nucleotide base at the end of each fragment was read according to its radioactive label
• if the first one base fragments had thymine at one end then the first base in the sequence is T
• if the two base fragments have a cytosine at the end, then the sequence is TC
• if the three base fragment ends with guanine then the base sequence is TCG

Question 3

What is biofromatic

Answer 3

• this has grown out of DNA sequencing to store the huge amounts of data generated
• would have been impossible to store and analyse these data prior to computers and microchips
• software packages are designed for this purpose

Question 4

Describe positives and negatives of Sangers sequencing apporach

Answer 4

• efficient and safe
• used it to sequence the genome of a phage virus called phi-X174, the first DNA based organism to have its genome sequences
• had to count off the bases one by one from the bands in a piece of gel this is very time consuming and therefore costly

Question 5

Describe cloning DNA

Answer 5

• gene to be sequenced was isolated using restriction enzymes from a bacterium
• the DNA was then inserted into a bacterial plasmid and then into an Escherichia coli bacterium host that when cultured, divided many time enabling the plasmid with the DNA insert to be copied many times
• each new bacterium contained a copy of the candidate gene
• these lengths of DNA were isolated using plasmid preparation techniques and were then sequenced

Question 6

Describe the first DNA sequencing machine

Answer 6

in 1986 the first automated DNA sequencing machine was developed at the California Institute of Technology based on Fred Sanger’s method

• Florescent 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 computer this method dispensed the need for technicians to read autoradiograms

Question 7

What is DNA sequencing

Answer 7

a technique that allows genes to be isolated and read

Question 8

describe and give an example of high throughput sequencing

Answer 8

• variety of approach used to develop fast, cheap methods to sequence genomes
• Pyrosequencing

Question 9

Describe synthetic biology

Answer 9

• synthetic biology is an interdisciplinary science concerned with designing and building useful biological devices and systems
• it encompasses biotechnology, evolutionary biology, molecular biology, systems biology and biophysics
• its ultimate goal may be to build engineered biological systems that store and process information, provide food, maintain human health and enhance the environment
• the sequences of DNA found by analysing genomes provide potential building blocks of synthetic biologists to build devices

Question 10

Describe bioethics

Answer 10

• synthetic biology raises ethical issues and biosecurity
• extensive regulations are already in place due to 30-40 years of genetically-modified organsism, there are many advisory panels and many scientific papers have been written on how to manage the risks
• synthetic biology is not about making synthetic life forms from scratch but is about a potential for new systems with rewards and associated risks to be managed

Question 11

Describe the human genome project

Answer 11

scientists predicted that the human genome would contain about 100,000 genes
- in 1990 the human genome was launched and the genome was sequenced by 2003, scientists were surprised to learn that it only contained 24,000 genes

Question 12

Describe the genome-wide comparison between individual and species

Answer 12

• whole genome sequencing determined the complete DNA sequence of an organisms genome, in the case of eukaryotic cells that is the genetic material of the chromosomes, mitochondria and if plants or algae, also of chloroplasts
• sequenced genomes are stored in gene banks

Question 13

Describe the comparisons between species

Answer 13

• when human genome was compared with those other species it became clear that very few human genes are unique to us
• most of our genes have counterparts in other organism
• we share over 99% of our genes with chimpanzees
• vertifies that genes that work well are conserved by evolution, for example pigs and genes have similar genes for insulin
• as evolution progresses some genes are co-opted to perform new tasks, tiny changes to a gene in humans called FOXP2 allows speech
• many differences between organisms is not because the organisms have totally different genes but because some of their shared genes have been altered and now work in subtly different ways
• some changes to the regulatory regions of DNA that do not code directly for proteins have also altered the expression of the genomes regulatory and coding genes interact in such ways that without increasing the number of genes, the number of proteins made may be increased

Question 14

Describe the evolutionary relationships

Answer 14

• comparing genomes of organisms thought to be closely related species has helped confirm their evolutionary relationships or has led to new knowledge about the relationships and in some cases to certain organism being reclassified
• DNA from bones and teeth of some extinct animals can be amplified and sequenced so that the animals evolutionary history can be verified

Question 15

Describe variation between individuals

Answer 15

• all humans are gentically similar expect of rare cases where a gene has been lost by deletion of part of a chromosome, we all have the same genes but we have different alleles
• about 0.1% of our DNA is not shared with others which sound small, but given that our genome contains 3 billion DNA base pairs this means that there are 3 million places on the DNA lengths where our DNA sequences can differ due to random mutations such as substitution
• places were these DNA substitutions occur are called single nucleotide polymorphisms or SNPs
• some have not effect on the protein and 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 regualting gene expression in eukaryotic cells
• methods to map methylation of a whole human genome can help researchers to understand the development of certain diseases for example certain types of cancer and why they may or may not develop in genetically similar individuals, the study of this aspect of genetics is called epigenetics

Question 16

Describe the development of DNA profiling

Answer 16

• 1978 Alec Jeffreys was locating tandem repeat sequence of DNA
• Tndem repeats are repetitive segments of DNA that do not code for proteins
• they may be between 10 and 100 base pairs long and they all deature teh same core sequence
• GGGCAGGAXG where X can be any one of the 4 nucletoide bases
• tandem repeats occur at more than 1000 locatiosn in the genome and in each of these places they may be repeated a random number of times some types are hihgly variable and are called variable number tandem repeats

Question 17

describe DNA profiling

Answer 17

1. DNA is obtained from the individual - either by a mouth swab from saliva on a toothbrush from blood or hair or bone
2. DNA is then digested with restriction enzymes, these enzymes cut the DNA at specific recognition sites, they will cut it into fragments which will vary in size from individual to individual
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 individuals is being compared is treated with the same restriction enzymes and also subjected to electrophoresis
6. the banding patterns of the DNA samples can then be compared

Question 18

what are the applications of DNA profiling

Answer 18

forensic science
maternity and paternity disputes
analysis of disease

Question 19

describe the types of DNA analysed

Answer 19

• first method involved restriction fragment lenght polymorphism analysis, this method is laborious and is no longer used
• today short tandem repeat (STR) sequences of DNA are used, these are highly variable short repeating lengths of DNA, the exact number of STRs varies from person to person
• STR sequence are separated by electrophoresis, each STR is polymorphic but the number of alleles in the gene pool for each one is small,
• 13 STRs are analysed simultaneously so although each STR is present in between 5% and 20% of individuals, the chances of two people sharing STR sequences at all the loci is 1x10 18 this is greater number than the number of people on earth
• technique is very senstive and even a trace of DNA is left when someone touches an object
• must be treated carefully to avoid contamination
• can be stored for many years if a crime case is unsolved it can then later be used to assess new evidence

Question 20

Describe forensic science

Answer 20

• brought about convictions and established the innocence of many suspects and of people previously wrongly convicted
• identify Nazi war criminals hiding in south america
• idenitfy the remians of romanov family and to refute a persons claim to be the survior
• lecsiter as Richard the 111

Question 21

Describe maternity and paternity disputes

Answer 21

• half of every childs genetic information comes from teh mother and half from the father, hence half the hsort tandem repeat STR fragmetns come from the mother and half from the father
• comapring the DNA profiles of mother, father and child can establish maternity and paternity

Question 22

Describe analysis of disease

Answer 22

protein electrophoresis can detect the type of haemoglobin present and aid diagnosis of sickle cell anaemia
- a varying number of repeat sequence for a condition such as huntington disease can be detected by electropherosis

Question 23

describe the PCR process

Answer 23

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 around 94-96 degrees celcius to break the hydrogen bonds between complementary nucleotide base pairs and thus denature the double stranded DNA into single strands of DNA
3. the mixture is cooled to around 68 degrees (or 50-60) so that primers can anneal to one end of each single strand of DA this gives a small section of a double stranded DNA at the end of each single stranded molecule
4. the Taq DNA polymerase enzyme molecules can now bidn to the end where there is a double strand DNA, Taq polyermase is obtained from a bacterium that lives at high temperatures 72 degrees is the optimum temperature for this enzyme
5. the temperature is raised to 72 degrees which keeps the DNA as single strands
6. the Taq DNA polyermase catalyses the addition of DNA nucleotides to the single stranded DNA molecules tarting at the end with the primer and proceeding in the 5 to 3 direction
7. when the Taq DNA polymerase reaches the other end of the DNA molecule then a new double strand of DNA has been generated
   8, the whole process begins again and is repeated for many cycles

Question 24

Describe applications of PCR

Answer 24

Tissue typing
donor and recipient tissues can be typed prior to transplantation to reduce the risk of rejection of the transplant

detection of oncogenes
if the type of mutation involved in a specific patients cancer is found then the medication may be better tailored to that patient

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 carry a recessive allele for a particular gene, fetal cells may be obtained from the mothers blood stream for prenatal genetic screening, during IVF treatment one cell from an 8 cell embryo can be used to analyse the fetal DNA before implantation

identifying viral infections
- senstitve PCR tests can detect small quantites of viral genome amongst the host cells DNA this can be used to verify HIV

monitoring the spread of infectious disease
- spread of pathogens through a population of wild or domestic animals or from animals to human populations, can be monitored and the emergence of new more virulent sub types can be detected

forensic science
- amplified for DNA profiling to identify criminals

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

Question 25

Describe the principles of PCR

Answer 25

- PCR amplifies the amount of DNA allowing it to be analysed - PCR is incroprotated into forensic DNA analysis and into the protocols for analysis of DNA for genetic diseases relies on the fact that - DNA is made of two antiparallel backbone strands - each strand of DNA has a 5 end and 3 end - dna grows only from 3 end - base pairs pair up according to complemetnary base pairings PCR differs from DNA replication in that - only short sequences of up to 10000 base pairs of DNA can be replciated not entire chromosomes - it requires the addition of primer molecules to make the process start - a cycle of heating and cooling is needed to separate the DNA strands, bind primers to teh strands and for the DNA strands to be replicated

Question 26

describe the PCR process

Answer 26

- tim conusming as teh DNA was heated to denature it and then cooled to around 35 degrees to anneal the primers and allow the DNA polymerase to work - later DNA polyermase was obtained from thermophilic bacterium and it was called Taq polymerase and is stable in high temperatures 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 around 94-96 degrees celcius to break the hydrogen bonds between complementary nucleotide base pairs and thus denature the double stranded DNA into single strands of DNA 3. the mixture is cooled to around 68 degrees so that primers can anneal to one end of each single strand of DA this gives a small section of a double stranded DNA at the end of each single stranded molecule 4. the Taq DNA polymerase enzyme molecules can now bidn to the end where there is a double strand DNA, Taq polyermase is obtained from a bacterium that lives at high temperatures 72 degrees is the optimum temperature for this enzyme 5. the temperature is raised to 72 degrees which keeps the DNA as single strands 6. the Taq DNA polyermase catalyses the addition of DNA nucleotides to the single stranded DNA molecules tarting at the end with the primer and proceeding in the 5 to 3 direction 7. when the Taq DNA polymerase reaches the other end of the DNA molecule then a new double strand of DNA has been generated 8, the whole process begins again and is repeated for many cycles

Question 27

What is electrophoresis

Answer 27

this is a process used to separate proteins of DNA fragments of different sizes - it can separate fragments by only one base pair and is used in gene technology to separate DNA fragments for identification and analysis

Question 28

How does Gel electrophoresis work

Answer 28

1. DNA samples are digested with restriction enzymes to cut them at specific recognition sites into fragments, this is carried out at 35-40 degrees and may take an hour 2. while the restriction enzymes are cutting the DNA tank is set up, agarose gel is made up and poured into the central region of the tank whilst combs are in place at one end, once the gel is set buffer solution is added which covers the gel and the end sections of the tank contain a buffer soltuion, now the comb can be carefully removed leaving wells at one end of the gel 3. A loading dye is added to the tubes containing the digested DNA 4. the digested DNA plus loading dye is added to the wells in the electrophoresis gel, to do this a pipette is used and this is held in the buffer solution just above one of the wells, the loading dye is dense and carries the DNA down into the well, pipette should not be placed right into the well otherwise you might pierce the bottom of the well 5. once all the wells are loaded with the different DNA samples the electrodes are put in place and connected to an 18v battery this is then left to run for 6-8 hours, or an alternative higher voltage power pack can be used and the gel runs for a shorter time of less than 2 hours, do not use hihger voltage unless the current is limited to 5mA or less otherwise there is a risk of severe electric shock from the electrodes or gel 6. DNA fragments move through the gel at different speeds smaller fragments travel faster so in a fixed period they travel further 7. 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

Question 29

How does the gel work in electrophoresis

Answer 29

- uses agarose gel plate covered by a buffer solution - electrodes are placed in each end of the tank so that when it is connected to a power supply an electric current can pass through the gel - DNA has an overall negative charge due to its many phosphate groups and the fragments migrate towards the anode - fragments of DNA have a similar surface charge regardless of their size

Question 30

How do you separate proteins

Answer 30

- same principle as separating DNA fragments, but it is carried out in the presence of a charged detergent such as sodium dodecyl sulfate - this equalises the surface charge on the molecules and allows the protein 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 change - used to analyse the types of haemoglobin proteins for diagnosis of conditions such as sickle cell anaemia, thalassamemia and leukaemia where patients have a higher than normal amounts of fetal haemoglobin

Question 31

How do you use DNA probes

Answer 31

- A DNA probe is short single stranded length of DNA that is complementary to a section of the DNA to be investigated DNA probe may be labelled using - a radioactive marker, usually with 32P in one of the phosphate groups in the probe strand, once the probe has annealed by complementary base pairing to the piece of DNA it can be revealed by exposure to photographic film - A fluorescent marker that emits a colour on exposure to UV light, fluorescent markers may also be used in automated DNA sequencing

Question 32

How do you use microarrays

Answer 32

scientists can place a number of different probes on a fixed surface known as DNA microarray - applying the DNA under investigation to the surface can reveal the presence of mutated alleles that match the fixed probes because sample DNA will anneal to any complementary fixed probes - the sample DNA must first be broken into smaller fragments and it may be amplified by PCR - DNA microarray can be made with fixed probes specific for certain sequences found in mutated alleles that cause genetic diseases in the well

Question 33

why are DNA probs good

Answer 33

they are useful in locating specific DNA sequences for example - to locate a specific gene needed for genetic engineering - to identify the same gene in a variety of different genomes from different species when conducting genome comparison studies - to identify the presence or absence of a specific allele for a particular genetic disease or that gives susceptibility to a particular condition

Question 34

How do you use microarrays

Answer 34

scientists can place a number of different probes on a fixed surface known as DNA microarray - applying the DNA under investigation to the surface can reveal the presence of mutated alleles that match the fixed probes because sample DNA will anneal to any complementary fixed probes - the sample DNA must first be broken into smaller fragments and it may be amplified by PCR - 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

Question 35

What are the principles of genetic engineering

Answer 35

- 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 organisms and inserted into another organism using suitable vectors

Question 36

what the stages necessary for genetic engineering

Answer 36

1. the required gene is obtained 2. a copy of the gene is placed inside a vector 3. the vector carries the gene into a recipient cell 4. the recipient expresses the novel gene

Question 37

TECHNIQUES IN GENETIC ENGINEERING: obtaining the required gene

Answer 37

- mRNA can be obtained from the cells where the gene is being expressed, the enzyme reverse transcriptase can then catalyse the formation of a single strand 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 whole base sequence codes for the original protein - if the scientists know the nucleotide sequence of the gene then the gene can be synthesised using an automated polynucleotide synthesiser - if scientists know the sequence of the gene they can design polymerise chain reaction primers to amplify the gene from the genomic DNA - a DNA probe can be used to locate a gene within the genome and the gene can then be cut out using restriction enzymes

Question 38

TECHNIQUES IN GENETIC ENGINEERING: placing the gene into a vector

Answer 38

- plasmids can be obtained from the organisms such as bacteira and mixed with restriction enzymes that will cut the plasmid at specific recognition sites - the cut plasmid has 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, DNA ligase helps the annealing (binding) - a gene may be sealed into an attenuated virus that could carry it into a host cell

Question 39

TECHNIQUES IN GENETIC ENGINEERING: getting the vector into the recipient cell

Answer 39

- heat shock treatment - if a bacteria are subjected to alternating periods of cold and heat in the presence of calcium chloride their walls and 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 - electroporation - high voltage pulse is applied to the cell to disrupt the membrane - electrofusion - electrical fields help to introduce DNA into the cells - transfection - DNA can be packaged into a bacteriophage which can then transfect the host cell - T1 plasmids are inserted into the bacterium which infects some plants and naturally inserts its genome into the host cell genomes

Question 40

TECHNIQUES IN GENETIC ENGINEERING: direct method of introducing gene into recipient

Answer 40

- if plants are not suspective to A. tumefaciens then direct methods can be used - small pieces of gold or tungsten are coated with DNA and shot into plants - this is called gene gun

Question 41

Describe reverse transcriptase

Answer 41

- reterovrisues such as HIV which contain RNA that they inject into the host genome have reverse transcriptase enzyme that catalyses the production of cDNA using their RNA as a template this is the reverse of trancription - useful for genetic engineering

Question 42

Describe restriction enzymes

Answer 42

- Bacteria and

Question 43

Describe reverse transcriptase

Answer 43

- reterovrisues such as HIV which contain RNA that they inject into the host genome have reverse transcriptase enzyme that catalyses the production of cDNA using their RNA as a template this is the reverse of transcription - useful for genetic engineering

Question 44

Describe restriction enzymes

Answer 44

- Bacteria and archaea have restriction enzymes called restriction endonucleases to protect them from attack by phage virsues - these enzymes cut up foreign viral DNA by a process called restriction preventing the viruses from making copies of themselves - prokaryotic DNA is protected from the action of these endonucleases by being methylated at recognition sites - the restriction endonucleases are named according to the bacterium from which they have been obtained - the first one used was EcoR1 number obtained from E.coli and was restriction endonuclease number 1 - restriction enzymes are useful to molecular biology and biotechnology as molecular scissors as they recognise specific sequences within a length of DNA and cleave the molecule there - some make a staggered cut leaving sticky ends others make a cut that produces blunt ends - not staggered

Question 45

Describe ligase enzymes

Answer 45

- used to join DNA fragments, catalyses a condensation reaction that joins the sugar groups and phosphate groups of the DNA backbone - enzymes catalyse reactions during DNA replication in cells and PCR

Question 46

How do you get insulin from GM bacteria

Answer 46

- scientists can obtain mRNA from beta cells of islets of langerhans in the human pancreas where insulin is made 1. add reverse transcriptase enzyme makes a single strand of cDNA 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. ligase enzymes help the insulin gene be inserted into plasmids extracted from the 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

Question 47

How do you make sure genetic engineering is carried out safely

Answer 47

- because bacteria have resistance to some antibiotics - we do not want them to escape from laboratories into the wild - they also have a gene knocked out which means they cannot synthesise a particular nutrient therefore they only survive in the laboratory where they are given that nutrient in their growth medium meaning that they cannot survive outside the lab

Question 48

What is the principle of gene therapy

Answer 48

- basic principle is to insert a functional allele of a particular gene into cells that contain only mutated an 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 - knowledge gained from the human genome project has led to furter possibilites such as using interference RNA to silence genes by blocking translation - used to treat AIDS

Question 49

describe somatic gene therapy

Answer 49

- gene therapy by inserting functional alleles into body cells - metabolic disorders such as cystic fibrosis occur when an individual inherits two faulty recessive alleles for a particular gene - this causes differentiated cells where this gene should normally be expressed lack the protein product of that gene - if functioning alleles for this gene can be put into specific cells so that these cells then can make the protein - these cells will function normally - various methods are available for delivering the functioning alleles to the patients body cells

Question 50

what is the outcome of somatic gene therapy

Answer 50

- affects only certain cell types, | - the alterations made to the patients genome in those cells are not passed to the patients offspring

Question 51

describe liposomes

Answer 51

- patients with cystic fibrosis lack a functioning CFTR gene - the alleles which are lengths of DNA can be packaged within small spheres of lipid bilayer to make liposomes - if these are placed into an aerosol inhaler and sprayed into the noses of patients some will pas 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 which is a transmembrane chloride ion channel - epithelial cells lining the respriatory tract have to be replaced every 10-14 days so this treatment has to be repeated at regular short intervals

Question 52

describe viruses

Answer 52

- have been used by 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 - in 1999 a patient taking part in a trial died and in 2002 some trials were interrupted after several patients developed leukaemia potential problems: - viruses even through not virulent may still provoke an immune or inflammatory response in the patient - the patient may become immune to the virus making subsequent deliveries impossible - the virus may insert the allele into the patient 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 patients genome in a location that disrupts the regulation of the expression of other genes

Question 53

describe artificial chromosomes

Answer 53

- research being carried out into the possibility of inserting genes into an artificial chromosome that would co-exist with other 46 chromosomes in the target cells

Question 54

Describe germ line therapy

Answer 54

- this is gene therapy by inserting functional alleles into gametes or zygotes - cells of the individual be altered but their offspring as well - potential to change genetic information of many people who have not given their conset - concerns of how the genes are inserted - may find their way into a location that could disrupt the expression or regulation of other genes and increase the risk of cancer - strict guideline drawn up

Question 55

what is DNA profiling

Answer 55

- some organisms genome consists of repetitive, non coding base sequences, these are sequences that dont code for proteins and repeat over and over - the number of times they repeat is different from person to person

Question 56

what is a transformed organism

Answer 56

- these are organisms that have had their DNA altered by genetic engineering

Question 57

what is recombinant DNA

Answer 57

- DNA vector and DNA fragment

Question 58

what is a vector

Answer 58

a vector is something that is used to transfer DNA into a cell - either plasmids or bacteriophages (viruses)

Question 59

describe electroporation

Answer 59

- suspension of the bacterial cells is mixed with the plasmid vector and placed in a machine called an electroporator - machine is switched on and an electrical field is created in the mixture which increases the permeability of the bacterial cell membranes and allows them to take in the plasmids this is called electroporation

Question 60

describe negative issues surrounding gene therapy

Answer 60

- used in other ways other than medical treatment - expensive - could have been used elswhere - somatic is short lived - undergo multiple treatments - diffiucult to get the allele into a specific body cell - body could identify vectors as foregin bodies and start immune response against them - allele could be inserted in teh wrong place - intersted allele could get overexpressed producing too much of the protien

Question 61

describe positive issues surrounding gene therapy

Answer 61

- prolong lives of people with genetic disorders giving them better quality of life - carriers with the genetic disorder may be able to conceive a baby without that disorder or risk of cancer - decrease the number of people that suffer from genetic disorders