Gene Technology Flashcards
Gene technology uses what? What are the 3 ways that they can be produced
DNA fragments
Can be produced using…
Reverse transcriptase
Restriction endonuclease
PCR
What is gene technology and examples. What are these techniques used for
All the techniques that can be used to study genes and their function
Examples…
Polymerase chain reaction (PCR)
In vivo gene cloning
DNA probes
Used for many things including DNA fingerprinting and diagnosing diseases
What are palindromic sequences of nucleotides
Sequences which consist of antiparallel base pairs
What does restriction endonuclease do
Recognises specific palindromic sequences (known as recognition sequences) and cut the DNA at these places. Different RE recognise different recognition sequences as the shape of the recognition sequence must be complementary to the enzymes active site. If recognition sequences are present at either side if the fragment, they cut here. The DNA sample is incubated with the specific RE and the fragment is cut out via a hydrolysis reaction. Sticky ends can be left, which can join the fragment to other pieces of DNA that has sticky ends with complementary sequences
What does reverse transcriptase do
Only 2 copies of gene in cells, but many complementary mRNA molecules. These used as templates to make complementary DNA (cDNA). mRNA isolated from cells, mixed with free nucleotides and reverse transcriptase
What is a sticky end
A small tail of unpaired bases at each end of the DNA fragment
What is the polymerase chain reaction used for
To make millions of copies of a fragment of DNA
What are primers
Short pieces of DNA that are complementary to the bases at the start of the fragment you want
What does DNA polymerase do
Creates new DNA strands
What is genetic engineering
The manipulation of an organisms DNA, also known as recombinant DNA technology
Transformed organisms are also known as….
Genetically engineered or genetically modified organisms
How can transformed organisms benefit agriculture
Can give higher yields or are more nutritious. Means plants can be used to reduce risk of famine and malnutrition. Crops can have pest resistance so fewer pesticides are needed. This reduces cost and environmental problems. Eg golden rice is a variety of transformed rice, contains 1 gene from maize plant and one from soil bacterium. Enable rice to produce beta-carotene. These are used in body to give vitamin A. Being developed in areas of world where vitamin A deficiency is a large problem
How can transformed organisms benefit industry
Industrial processes often use biological catalysts (enzymes). These enzymes can be produced from transformed organisms so they can be produced in large quantities for less money. Eg rennin is enzyme used in cheese making, used to make rennet (Substance made in cows stomachs). Can now be made from transformed organisms so can be made in large quantities cheaply and no harm to cows
How can transformed organisms benefit medicine
Many drugs and vaccines produced by transformed organisms so can be produced quickly, cheaply and in large quantities. Eg insulin (used to treat type 1 diabetes) used to come from animals. This insulin wasn’t human insulin so didn’t work as well. Human insulin now made from transformed organisms using a cloned human insulin gene
What are the concerns about the use of genetic engineering to agriculture
Farmers might plant only one type of transformed crop (monoculture) makes whole crop vulnerable to disease as plants genetically identical
Some people concerned about superweeds, weeds that are resistant to herbicides. These could occur if transformed crops interbreed with wild plants
What are the concerns of genetic engineering to industry
Without proper labelling, some people think they won’t have a choice about whether to consume food made using genetically engineered organisms. Some are worried that the process used to purify proteins could lead to the introduction of toxins into food industry
What are the concerns of genetic engineering to medicine
Companies who own genetic engineering technologies may limit the use of technologies that could save lives. Some worry this technology could be used unethically eg make designer babies
What do humanitarians think about genetic engineering
crops could be produced that help reduce risk of famine and malnutrition
Transformed crops could be used to produce useful pharmaceutical products eg vaccines which could make drugs available to more people
Medicines could be produced more cheaply so more can afford them
What do environmentalists and anti-globalisation activists think about genetic engineering
Environmentalists oppose recombinant DNA technology as they think it could potentially damage environment. Eg transformed crops could encourage farmer to carry out more monoculture, decreasing biodiversity. Also fears of superweeds
Anti-globalisation activists think a few large biotechnology companies control some forms of genetic engineering. As the use of this technology increases the companies get bigger and more powerful. May force smaller businesses out of business
How are anti-globalisation activists
People who oppose globalisation (growth of large multinational companies at the expense of smaller ones)
What are genomes
All the genetic material in an organism
What are repetitive non-coding base sequences
Base sequences that don’t code for proteins and repeat next to each other over and over
How can genetic fingerprinting be used to determine genetic relationships?
We inherit the repetitive, non-coding base sequences from parents. Roughly half of sequences come from each parent. Means the more bands on genetic fingerprint that match, the more closely related 2 people are.
How can genetic fingerprinting be used to determine genetic variability within a population?
The greater the number of bands that don’t match, the more genetically different people are. Means you can compare number of repeats at several places in the genome for a population to find out how genetically varied that population is eg the more the number of repeats varies at several places, the greater the genetic variability
Genetic fingerprinting can be used in forensic science. Explain…
Used to compare samples of DNA collected from crime scenes (eg DNA from hair, blood, skin cells)
Genetic fingerprinting can be used in medical diagnosis. Explain…
A genetic fingerprint can refer to a unique pattern of several alleles. Can be used to diagnose genetic disorders and cancer. Useful when the specific mutation isn’t known or where several mutations could have caused the disorder as it identifies a broader, altered genetic pattern.
Example- PGH screens embryos created by IVF for genetic disorders before they’re implanted into uterus. Faulty regions of parents DNA used to produce genetic fingerprints which are compared to the genetic fingerprint of the embryo. If fingerprints match, embryo has inherited disorder eg cystic fibrosis
Genetic fingerprinting can be used in animal and plant breeding. Explain…
Genetic fingerprinting can be used on animals and plants to prevent inbreeding which causes health, productivity and reproductive problems. Inbreeding decreases gene pool which can lead to increased risk of genetic disorders, leading to health problems. Genetic fingerprinting can be used to identify how closely related individuals are , the more closely related 2 individuals are, the more similar their genetic fingerprint. The least related individuals will be bred together
The base sequence of a gene can be determined by….
Restriction mapping and gene/DNA sequencing
What is the purpose of restriction mapping
Genes are too long to be sequenced all in one go, so they’re cut into smaller sections using restriction enzymes. The smaller sections are then put back in the correct order so the entire gene sequence can be read in the right order
What is the purpose of gene/DNA sequencing
Used to determine the order of bases in a section of DNA. Can be carried out by the chain termination method, which lets you sequence small fragments of DNA
What is sickle-cell anaemia
Recessive genetic disorder caused by a mutation in the haemoglobin gene. The mutation causes an altered haemoglobin protein to be produced, makes red blood cells sickle-shaped (concave). These red blood cells block capillaries, restrict blood flow, causing organ damage and periods of acute pain. Some people are carriers of the disease (carry only 1 recessive allele). Sickle-cell carriers are partially protected from malaria-this advantageous effect has caused an increase in the freq of the sickle-cell ale in areas where malaria is common. However, this increases the likelihood of people in these areas having the disease so more suffer
DNA probes can be used to…
Locate genes or see if a persons DNA contains a mutated gene
2 ways that DNA probes can work to screen for mutated genes are…
The probe can be labelled and used to look for a single gene in a sample of DNA
OR
the probe can be used as part of a DNA microarray which can screen for lots of genes at the same time
What is a DNA microarray
A glass slide with microscopic spots of different DNA probes attached to it in rows. Sample of labelled human DNA washed over it. If the human DNA contains DNA sequences that match the probes, it sticks to the array. Array is washed to remove any labelled DNA that hasn’t stuck. Array visualised under UV light. Any labelled DNA attached to probe fluoresces. Spots that fluoresce mean that person’s DNA contains that specific gene
What is genetic counselling
Advising patients and relatives about the risks of genetic disorders.
What does genetic counselling involve?
Advising people about screening and explain the results of a screening. Screening can help to identify the carrier of a gene, the type of mutated gene they’re carrying and the most effective treatment. If the results are positive then genetic counselling is used to advise the patient on the options of prevention or treatment available
The results of screening can be used for…
Genetic counselling and deciding treatment
How does gene therapy work
Involves altering defective genes inside cells to treat genetic disorders and cancer. How you do this depends on whether the disorder is caused by a mutated dominant allele or 2 mutated recessive alleles
In gene therapy, how is the new allele inserted into the new cells
Inserted into cells using vectors. Different vectors can be used eg altered viruses plasmids or liposomes
What are liposomes
Spheres made of lipid
What are the 2 types of gene therapy
Somatic
Germ line therapy
What is somatic therapy
Involves altering the alleles in body cells, particularly the cells that are most affected by the disorder. Eg cystic fibrosis is a genetic disorder that’s damaging to the respiratory system so somatic therapy targets the epithelial cells lining the lungs. The therapy doesn’t affect the individuals sex cells, so offspring could inherit disease
What is germ line therapy
Involves altering the alleles in the sex cells. Means that every cell of any offspring produced from these cells will be affected by the gene therapy and they won’t suffer from the disease. The therapy is currently illegal in humans
Ethical issues with gene therapy include…
Some people are worried that the technology could be used in ways other than for medical treatment eg treating the cosmetic effects of ageing
Others worry that there is the potential to do more harm than good y using the therapy
Advantages of gene therapy
Could prolong the lives of people with genetic disorders or cancer
Could give these people a better quality of life
Carriers of genetic disorders might be able to conceive a baby without that disorder or risk of cancer (only in germ line)
Could decrease the number of people that suffer from genetic disorders and cancer (only in germ line)
Disadvantages of gene therapy
The effects of the treatment may be short-lived (only in somatic)
Patient might have to undergo multiple treatments (only in somatic)
Might be difficult to get the allele into specific body cells
Body could identify vectors as foreign bodies and start an immune response against them
An allele could be inserted into the wrong place in the DNA, could cause more problems
An inserted allele could get over-expressed, producing too much of the missing protein
Disorders caused by multiple genes (eg cancer) would be difficult to treat with this technique
Explain the process of PCR
Reaction mixture of DNA sample, primers, DNA polymerase and fee nucleotides. Mixture heated to 95c to break hydrogen bonds between the strands of DNA. Then cooled to 55c so primers can bind to strands. Then heated to 72c so DNA polymerase can work. It lines up free nucleotides alongside each template strand. SBP means complementary strands are formed. 2 new copies of DNA fragment formed. Cycle starts again
What are the 2 different ways that gene cloning can be carried out?
In vivo
OR
In vitro
What is gene cloning
Making loads of identical copies of a gene
What is in vitro cloning
Where the gene copies are made outside of a living organism using PCR
What is in vivo cloning
Where the gene copies are made within a living organism. As the organism grows and divides, it replicates its DNA, creating multiple copies of the gene
What are transformed organisms
Organisms that have had their DNA altered by genetic engineering
What is recombinant DNA
DNA formed by joining together DNA from different sources
What are the 3 temperatures involved in PCR
90c
55c
72c
What is a vector
Something that’s used to transfer DNA into a cell
Can be plasmids, bacteriophages
What are bacteriophages
Viruses that infect bacteria
Advantages and disadvantages of in vivo cloning
Can produce mRNA and protein as well as DNA as its done in living cell. Can also produces modified DNA, RNA or protein (they have modifications added to them)
Large DNA fragments can be cloned
Cheap, depending on how much DNA you want to produce
The fragment has to be isolated from other cell components= slow
Advantages and disadvantages of in vitro cloning
Used to make lots of copies of DNA
The DNA produced isn’t modified
Only replicates the fragment of interest so don’t have to isolate fragment from other cell components
Fast
Can only replicate a small DNA fragment
mRNA and protein not made
Expensive if want to produce large amount
What is genetic engineering
The manipulation of an organisms DNA. Also called recombinant DNA technology
What are transformed organisms
Organisms that have had their DNA altered by genetic engineering. They have recombinant DNA
What technique is used to make a genetic fingerprint
Electrophoresis-it separates DNA fragments
What can genetic fingerprinting be used for
Determining relationships and variability within a population
Forensics
Medical diagnosis
Animal and plant breeding
What are DNA probes
Short strands of DNA. Have specific base sequence that’s complementary to base sequence of part of target gene
What is a restriction map
A diagram of a piece of DNA showing the different cut sites
What is a partial digest
In restriction mapping, where the restriction enzymes haven’t been left long enough to cut at all of their recognition sequences, so produces fragments of other lengths
How do you make a DNA probe
The gene that you want to screen for is sequenced. PCR makes copies of the gene-these are the probes
