Manipulating genomes Flashcards
what are some techniques for studying genes?
- the polymerase chain reaction (PCR)
- cutting out DNA fragments using restriction enzymes
- Gas electrophoresis
how can PCR be used to study genes?
-PCR can be used to select a fragment of DNA (containing the gene or bit of DNA you’re interested in) and amplify it to produce millions of copies in jut a few hours
what is the 1st of the polymerase chain reaction (PCR)?
1- A reaction mixture is set up hat contains the DNA sample, free nucleotides, primers and DNA polymerase. primers are short pieces of DNA that are complementary to the bases at the start of the fragment you want. DNA polymerase is an enzyme that creates new DNA strands.
what is the 2nd of the polymerase chain reaction (PCR)?
2- the DNA mixture is heated to 95 degrees to break the hydrogen bonds between the 2 strands of DNA. DNA polymerase doesn’t denature even at this high temp- this is important as it means many cycles of PCR can be carried out without having to use new enzymes each time. The mixture is then cooled to 50-65 degrees so that the primers can bind to the strands.
what is the 3rd of the polymerase chain reaction (PCR)?
3- the reaction mixture is heated to 72 degrees, so DNA polymerase can work. The DNA polymerase lines up free DNA nucleotides alongside each template strand. Complementary strands are formed.
what is the 4th of the polymerase chain reaction (PCR)?
4- two new copies of the fragment of DNA are formed and one cycle of PCR is complete. Then the cycle starts again- the mixture is heated to 95 degrees and this time all 4 strands (two original and two new) are used as templates
how do we use restrictive enzymes to study genes?
- restrictive enzymes recognise specific palindromic sequences (known as recognition sequences) and cut (digest) the DNA at these places.
- different restrictive enzymes cut at different specific recognition sequences, because the shape of the recognition sequence is complementary to an enzyme’s active site
- the DNA sample is incubated with the specific restriction enzyme, which cuts the DNA fragment via hydrolysis reaction
- Sometimes the cut leaves sticky ends (small tails of unpaired bases at each end of the fragment. Sticky ends can be used to bind to the DNA fragment to another piece of DNA that has sticky ends with complementary sequences
what is electrophoresis?
it’s a procedure that uses an electrical current to separate out DNA fragments, RNA fragments or proteins depending on their size
what has to be done with RNA fragments and proteins before you carry out electrophoresis?
-proteins can be positively charged or negatively charged is, before they undergo electrophoresis, they’re mixed with a chemical that denatures the proteins so they all have the same charge.
give an example of a use for the electrophoresis of proteins?
-to identify the proteins present in the urine or blood samples, which may help to diagnose disease
whats a DNA profile?
when you use electrophoresis to analyse the number of times a sequence is repeated at different, specific places (loci) in a person’s genome (and so the number of nucleotides there
how are DNA profiles used in forensic science?
- DNA is isolated from all the collected samples
- PCR is used to amplify multiple areas containing different sequence repeats- primers are used to bind to either side of these repeats and so the whole repeat is amplified
- the PCR products are run on an electrophoresis gel and the DNA profiles produced are compared to see if any match
- if the samples match, it links a person to the crime scene
how are DNA profiles used in medical diagnosis?
- a DNA profile can refer to unique pattern of several alleles. It can be used to analyse the risk of genetic disorders.
- its useful when the specific mutation isn’t known or where several mutations could have caused the disorder, because it identifies a broader, altered genetic pattern.
what is genetic engineering?
the manipulation of an organism’s DNA
- genetic engineering involves extracting a gene from organism and then inserting it into another organism (often one thats a different species)
- genes can be manufactured instead of bein extracted from an organism
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 is a transgenic organism?
-an organism that has been genetically engineered to include a gene from a different species
describe part 1 of genetic engineering
-get hold of a DNA fragment that contains the desired gene. The fragment can be isolated from another organism using restriction enzymes
describe part 2 of genetic engineering
step 1:
-the vector DNA is isolated
step 2:
-the vector DNA is cut open using the same restriction enzyme that was used to isolate the DNA fragment containing the desired gene. This means that the sticky ends of the vector DNA are complementary to the sticky ends of the DNA fragment containing the gene.
step 3:
-The vector DNA and DNA fragment are mixed together with DNA ligase. DNA ligase joins the sugar-phosphate backbones of the 2 bits of DNA. This process is called ligation.
step 4:
-The new combination of bases in the DNA (vector DNA + DNA fragment) is called recombinant DNA.
whats a vector?
a vector is something that’s used to transfer DNA into a cell
whats a plasmid?
small, circular molecules of DNA in bacteria
whats a bacteriophage?
viruses that infect bacteria
describe part 3 of genetic engineering
- the vector with the recombinant DNA is used to transfer the gene onto the bacterial cells (host cells). If a plasmid vector is used, the host cells have to be persuaded to take in the plasmid vector and its DNA.
- With a bacteriophage vector, the bacteriophage will infect the host bacterium by injecting its DNA int it. The phage DNA (with the desired gene it it) then integrates into the bacterial DNA.
- cells that take up the vectors containing the desired gene are genetically engineered, so are called transformed.
how do you create insect resistant plants?
one way in which plants can be genetically manipulated is by having a gene inserted into their cells which makes them resistant to insect pests
what are some positive ethical issues concerning GM soybean plants?
- they will reduce the amount of chemical pesticides the farmers use on their crops, which can harm the environment
- GM plants can also be designed to be more nutritious
what are some negative ethical issues concerning GM soybean plants?
- farming GM soybean plants may encourage monoculture–> decreases biodiversity and could leave the whole crop vulnerable to disease because all the plants are genetically identical
- there’s a risk that GM soybean plants could interbreed with wild plants creating ‘superweed’- weeds that are resistant to herbicides
whats ‘pharming’?
producing pharmaceuticals (medicinal drugs) using genetically modified organisms, such as animals
what are some positive ethical issues concerning ‘pharming’?
-drugs made this way can be made in large quantities compared to other methods of production. This can make them more available to more people.
what are some negative ethical issues concerning ‘pharming’?
- concern that manipulating an animal’s genes could cause some harmful side effects for the animal
- treating an animal in this way is enforcing the idea that animals are merely ‘assets’ that can be treated however we choose
what is a positive ethical issue concerning using pathogens for research?
-previously untreatable diseases can now be treated, reducing the suffering they would cause
what are some negative ethical issues concerning using pathogens for research?
- some people are worried that the scientists researching the pathogens could be infected with the live pathogen and potentially cause a mass outbreak of disease
- some people are concerned that the genetically modified version of a pathogen could revert back to its original form and cause an outbreak of disease
- some people worry that in the wrong hands, knowledge of how to genetically engineer dangerous pathogens could be used maliciously to create agents fro biowarfare
what are some positive ethical issues concerning ownership of GM organisms?
-the owner of the patent will get get money generated from selling the product which encourages scientists to compete to be the frist to come up with a new, beneficial idea= faster
what are some negative ethical issues concerning ownership of GM organisms?
-farmers in poorer countries may not be able to afford patented genetically modifies seeds + even if they can afford the seeds for a year they’re not allowed to plant ad grow any of the seeds from that crop again without paying again= unfair
how does gene therapy work?
gene therapy involves altering alleles inside cells to cure genetic disorders.
- if it’s caused by two mutated recessive alleles you can add a working dominant allele to make up for them- you supplement the faulty ones
- if it’s caused by a mutated dominant allele you can ‘silence’ the dominant allele
what are the 2 types of gene therapy?
- somatic therapy
- germ-line therapy
how does somatic therapy work?
- somatic therapy involves altering the alleles in the body cells that are most affected by the disorder.
- somatic therapy doesn’t affect the individual’s sex cells though, so any offspring could still inherit the disease
how does germ line therapy work?
- this involves altering the alleles in the sex cells. This means that every cell of any offspring produced from these cells will be affected by the gene therapy and they won’t inherit the disease
- germ line therapy in humans is currently illegal
what are some positive ethical issues of gene therapy?
- gene therapy could prolong the lives of people with life- threatening genetic disorders
- gene therapy could give people with genetic disorders a better quality of life if it helps to ease symptoms
- germ line therapy would allow the carriers of genetic disorders to conceive a baby without that disorder
- germ line therapy could decrease the number of people that suffer from genetic disorders and cancer, which is beneficial for individuals and society as a whole (as fewer people will require treatment)
what are some negative ethical issues of gene therapy?
- the tech could potentially be used in ways other than for medical treatment, such as for treating the cosmetic effects of ageing
- risk of overexpression of genes
- there’s a concern that gene therapy is expensive -some people believe that health services resources could be better spent on other treatments that have passed clinical trials
what are some disadvantages of gene therapy?
- the body could identify vectors as foreign bodies and start an immune system
- an allele could be inserted into the wrong place in the DNA potentially causing more problems
- an inserted allele could get overexpressed, producing too much of the missing protein, and so causing other problems
- the effects of the treatment may be short lived in somatic therapy
- the patient might have to undergo multiple treatments with somatic therapy
- it might be difficult to get the allele into specific body cells
what is a method used to determine the order of bases in a section of DNA?
chain termination method
