genetic engineering Flashcards
BRCA1 and BRCA2 gene
produce tumour suppressor portions and when faulty increase chances of ovarian and breast cancer
pros of genetic screening for people with family history BRCA1/2 gene mutations
a person may decide to take preventative measures like elective mastectomy
screening for breast cancer may start earlier to happen more frequently and the individual will have more frequent clinical examinations of the ovaries
person can participate in research clinical trials
advantage of genetic screening for Huntington’s
gives people a chance to plan for the future- how they will live and be cared for
couple can make informed reproductive decisions ( their child will have a 50% chance of inheriting the disease)
people can participate in research and clinical trials
huntingtons symptoms
lower cognitive ability and uncontrolled movements
is Huntington dominant or recessive
dominant
is cystic fibrosis (CF) dominant or recessive
recessive
CF is a mutation in which gene
a gene that codes for a transported protein CFTR
what is cystic fibrosis
a progressive disease that causes mucus in various organs to become thick and sticky. a common cause of death is bacteria infection in the lungs
what does the mutation in the gene coding for the protein CFTR cause
CFTR no longer transports chloride ions across the cell plasma membranes so water does not move by osmosis across the membrane either. Water makes the mucus thinner enabling cilia to remove it
advantage of genetic screening for CF
allows couples to make informed reproductive decisions (both may be carriers that do not display any symptoms)
people can participate in research and clinical trials
7 advantages of using bacteria, yeast and cultures of mammalian cells to produce recombinant proteins like insulin factor VII and adenosine deaminase
production facilities do not require much space
process can be carried out anywhere in the world
More cost-effective to produce large volumes (i.e. there is unlimited availability)
Simpler (with regards to using prokaryotic cells)-simple nutritional requirements
Faster to produce many proteins
Reliable supply available
The proteins are engineered to be identical to human proteins or have modifications that are beneficial
It can solve the issue for people who have moral, ethical or religious concerns against using cow or pork-produced proteins
Insulin
conjugation
transfer of genetic material from one bacterium to another
how to make recombinant human insulin protein
Bacteria plasmids are modified to include the human insulin gene using restriction endonuclease and DNA ligase.
Plasmids are inserted into the bacterium Escherichia coli by transformation (bath of calcium ions then heat/electrical shock)
Once the transgenic bacteria are identified (by the markers), they are isolated, purified and placed into fermenters that provide optimal conditions
The transgenic bacteria multiply by binary fission and express the human protein - insulin, which is eventually extracted and purified
transduction
gene transfer of genetic material form one bacterium to another via a virus
How can you make recombinant cells producing facer VII
Kidney and voerman hamster cells have been genetically modified to produce Factor VII
The recombinant. cells a placed in a fermentor and cultured
due to the optimal conditions in the fermenter the hamster cells constantly express Factor VII which can be extracted purified and used as injectable treatment for haemophilia
Fewer ethical, moral or religious concerns (proteins are not extracted from human blood)
Less risk of transmitting infection (eg. HIV) or disease
Greater production rate
what does adenosine deaminase do
it is an enzyme that breaks down deoxyadenosine which can be toxic to cells such as T-lymphocytes.
how to make recombinant cells that produces ADA
The larva of the cabbage looper moth (Trichoplusia ni) has been genetically modified (using a virus vector) to produce the enzyme adenosine deaminase so that it can be used as a treatment whilst the patients wait for gene therapy or when gene therapy is not possible
Fewer ethical, moral or religious concerns (proteins are not extracted from cows)
Less risk of transmitting infection or disease (from cows)
More reliable production of the enzyme
Faster to produce many proteins
what is SCID (serve combined immunodeficiency)
you have ADA (adenosine deaminase deficiency) and the immune system is damaged
genetic screening
testing for an embryo foetus or adult to find out whether a particular allele is present
possibilities of gene therapy
replace or inactivate a faulty gene or insert a new one
gene therapy
treatment of a genetic disorder by inserting genetically corrected cells into the body or introducing functioning genes directly into affected cells
what is Leber congenital amaurosis
a rare form of blindness
non viral vectors
liposomes and ‘naked DNA’
why are most gene therapies still in clinical trial stages
its hard to find delivery systems that can transfer normal alleles into a persons cell and ensure the gene is correctly expressed once there
2 types of somatic gene therapy
Ex vivo – the new gene is inserted via a virus vector into the cell outside the body. Blood or bone marrow cells are extracted and exposed to the virus which inserts the gene into these cells. These cells are then grown in the laboratory and returned to the person by an injection into a vein
In vivo – the new gene is inserted via a vector into cells inside the body
SCID treatment
ex vivo somatic gene therapy
During this therapy
a virus transfers a normal allele for ADA into T-lymphocytes removed from the patient and the cells are then returned via an injection
Why is SCID treatment not permanent
the T-lymphocytes are replaced naturally over time and therefore the patient requires regular transfusions every three to five months to keep their immune systems functioning
why are retroviruses no longer used as vectors for scid treatment
retrovirus insert their genes randomly into a host’s genome which means they could insert the gene into another gene or into a regulatory sequence of a gene (which could result in cancer)
Initial treatments did cause cases of leukaemia in children, so researchers switched to using lentiviruses or adeno-associated viruses as vectors
difference between lentiviruses and adenosine-associated viruses
Lentiviruses also randomly insert their genes into the host genome however they can be modified to not replicate, whereas adeno-associated viruses do not insert their genes into the host genome and therefore the genes are not passed onto the daughter cells when a cell divides
This is an issue with short-lived cells like lymphocytes but has not been a problem when used with longer-living cells such as liver cells
treatment for leber congenital amaurosis
There is no cure for these diseases
Using in vivo somatic gene therapy, doctors injected into the retina adeno-associated viruses that contained the normal alleles of one of the genes that caused damage to the photoreceptors
All patients that have had the injections have shown improvement in their eyesight
pre-implantation genetic diagnosis (PGD)
embryos that are created outside the body via IVF can have their DNA analysed allowing for embryos that are not carrying harmful allele to be chosen for implantation
How can genetic screening lead to a miscarriage
due to the procedures used to collect DNA which are not 100% risk-free
Amniocentesis – is used to obtain a sample of amniotic fluid using a hypodermic needle at 15 to 16 weeks of pregnancy
Chorionic villus sampling – is used to obtain a small sample of the placenta using a needle between 10 and 13 weeks of pregnancy
social and ethical considerations of using gene therapy
The potential for side effects that could cause death (e.g. the children who were treated for SCID developed leukaemia)
The commercial viability for pharmaceutical companies – if it is a rare disease, the relatively small number of patients may not mean that the companies will make a profit
The expense of treatments as multiple injections of the genes may be required if the somatic cells are short-lived (e.g. severe combined immunodeficiency)
This may make the cost of gene therapy accessible to a limited number of people
The possibility that people will become less accepting of disabilities as they become less common
Who has the right to determine which genes can be altered and which cannot (e.g. should people be allowed to enhance intelligence or height)
Another method of enhancing sporting performances unfairly through gene doping
This is where the genes are altered to give an unfair advantage eg. to provide a source of erythropoietin (the hormone that promotes the formation of red blood cells)
Test yourself
structural genes
codes for a protein that has a role with in the cell
transcription factors
proteins that bind o DNA and are involved in the control of the gene expression in eukaryotes by decreasing/increasing rate of transcription
inducible enzyme
only synthesised when substrates their are present
regulatory gene
codes for a protein that controls the expression of another gene
repressible enzyme
synthesised as normal until a repressor protein bind to operator
lac Z
codes for permeate gene that allows lactose to enter cell
lac z
codes for B galactosidase which breaks lactose into galactose and glucose
operon
functional unit of transcription. A cluster of genes that are controlled by the same promoter
transcription factors in eukaryotes
responsible for determination of sex in mammals
form part of protein complex that binds to the promoter region of the gene concerned
development of baby in womb
allow responses to environmental stimuli such as turning on right genes to respond to high temps
regulate cell cycle
how to TF affect development of baby in womb
ensure a number of different genes are activated in the correct sequence allowing correct pattern of development od boggy regions as a zygote becomes an embryo then feuds
what is gas 9
an endonuclease that cuts DNA at a specific point determined by guide DNA (gRNA). Part of gRNA can locate and bind to complementary DNA. Cas9 is an enzyme with 2 active sites for both strands of DNA
what is CRISPR
group of base sequences that code for a short length of RNA, they direct a nuclease enzyme (caS 9) towards a specific base sequence.
pcr temps
denaturation 95
annealing 60
extension 72
why do you use microarrays
identify genes present in organisms genomes and and out which are expressed
study large number of genes in a short time
Purpose of pcr
Amplify DNA/ produce many identical strands
Purpose of primers
Short single strand of DNA that Binds to the start of a desired gene so that DNA polymerase enzyme can begin copying
Why are VNTRs useful for carrying out genetic fingerprints
The length of VNTR varies between people only identical twins have the same lengths
Vector definition
Carrier of DNA into another cell
Where is human insulin mRNA extracted from
Human pancreatic cells
3 reasons why use genetic engineering over selective breeding
organisms with the desired trait are produced more quickly
all organisms will contain the desired characteristics (no chance recessive allele will arise in population
the desired characteristic may come from a different species/kingdom
gm salmon
gm to grow more rapidly by inserting a gene from chinook salmon with promotor gene from ocean pout so growth hormone is produced the whole year not just spring and summer
how to prevent gm salmon form reproducing in the wild
only gm females and sterile salmon
gm soybean
gene from agrobcterium that is herbicide resistant by allowing enzyme to produce amino acids that make proteins in growing tips.
The herbicides inhibits the enzyme in plants without the resistant gene; without the proteins being synthesised, the plants die
which 3 amino acids are made by enzymes form agrobacterium
phenylalanine, tyrosine and tryptophan
gm maize
Maize has been genetically modified with a gene for the Bt toxin, which is taken from the bacterium Bacillus thuringiensis and produce their own insectiside
When an insect ingests parts of the maize plant, the alkaline conditions in their guts activate the toxin (the toxin is harmless to vertebrates as their stomach is highly acidic), killing the insect
Different strains of B. thuringiensis produce different toxins which are toxic to different insect species
Insect populations have developed resistance to the genes for Bt toxin, reducing effectiveness as a means of protecting crops
process of genetic screening
1.patient DNA is isolated
2.DNA is amplified using PCR
3.restriction endonuclease used to cut up DNA into smaller fragments
4.Fragments under go gel electrophoresis
5.Dna fragments transferred to Nylon membrane and probes added to sample
6.gel washed and UV shone
2 techniques to obtain cells from a growing foetus to undergo genetic screening
amniocentesis
chronic villus sampling
why is gene delivery difficult to implement
difficulty inserting allele to replace faulty ones
lack of suitable vector
only short term relief
