Genetic Engineering Flashcards
What is genetic engineering?
The direct manipulation of an organisms genes involving:
- Addition or removal of genes.
- Silencing of genes by blocking gene expression.
Examples of reasons for genetic engineering.
- Modifying bacteria and eukaryotic cells to make special chemicals that are only produced in small quantities by other methods.
- Making crop plant resistant to diseases, pests and herbicides.
- Making livestock resistant to diseases and pests.
- Improving the yields from crop plants and livestock.
- Modifying animals to make human proteins for medicines that are difficult to obtain by other methods.
Enzymes involved in genetic engineering.
Reverse transcriptase - RNA made into DNA (reverse of transcription).
DNA ligase - used to join pieces of DNA together to make recombinant DNA (DNA that is joined from different organisms).
Restriction endonuclease - recognise and cut DNA. Restriction sequences are about 6 bases long. DNA produces complimentary single stranded DNA sticky ends. E.g insulin gene isolated from a pancreas cell using restriction enzyme. This leaves sticky ends.
First stage of genetic engineering - what are the options?
Obtain the gene of interest.
A) if you don’t know sequence of gene -> extract mRNA, use reverse transcriptase to make single stranded cDNA. Use DNA polymerase to make it double stranded.
B) If you know the sequence of gene.
- It can be produced using an automatic synthesiser.
- You can amplify the gene from genomic DNA using PCR.
- You can cut it out of genomic DNA using restriction enzymes.
Second stage of genetic engineering - what are the options?
Vector - insert gene into a vector
A) seal into a virus.
B) use a bacterial plasmid.
- Cut the plasmid with restriction enzymes.
- This leaves sticky ends.
- Cut the gene with the same restriction enzymes.
- This leaves complimentary sticky ends.
- Use DNA ligase to anneal.
Third stage of genetic engineering - what are the options?
Insert vector into cell
A) Heat 1 cold shock (with calcium chloride, CaCl2).
B) Electroporation - cells are exposed to electric pulses.
C) Electrofusion - use of an electrical field.
D) Transfection - Inserted into bacteriophage,
E) Ti plasmid - Inserted into agrobacterium which affects plants.
Fourth stage of genetic engineering.
OR directly insert gene into a cell
- Gold or tungeston is coated with DNA and shot into plant cells using a gene gun.
Fifth stage of genetic engineering.
Transformation - genetic markers.
- Known as marker gene.
- Used to identify when cells have taken up the vector containing the new gene.
- Usually antibiotic resistant genes such as tetracycline.
- Marker genes inserted with new gene.
- Bacteria grown on selective medium.
- Only bacteria with resistant gene will grow.
What do vectors do and examples of vectors?
- Used to transfer or carry genes.
Bacterial plasmids - non chromosomal pieces of DNA -> can be removed from bacteria cell then put back.
Viruses - Can carry genes into other organisms such as bacteria and animals. The virus can be directly transferred into the target cells. - Yeast cell chromosomes.
Inserting genes into cells.
- Heat 1 cold shock.
Microinjection - DNA is injected directly through cell and nuclear membrane using a micropipette.
Liposomol - artificial vesicles made of phospholipid and cholesterol are used to package DNA. They fuse with the cell membrane to deliver DNA to target cells.
Electroporation - cells are exposed to electric pulses that disrupt the membrane to deliver DNA to target cells.
How do you use reverse transcriptase?
- Find a cell that produces protein you require.
- Extract mRNA from the cells.
- Reverse transcriptase makes DNA from RNA.
Advantage and disadvantage of pest resistance.
Ad -> inc yield, protects environment, helps for farmers.
Dis -> pests become resistant.
Disease resistant ad and dis
Ad- inc yield
Dis- genes transferred to wild populations.
Herbicide resistance. Ad and dis
Ad - inc yield -> reduces competition.
Dis - lowers biodiversity.
Extended shelf life ad and dis
Ad - reduces food waste.
Dis - reduces commercial value
Nutritional value ad and dis
Ad - increased vitamins
Dis - allergic reactions
Medical uses ad
Medicine/vaccine production
Why can’t LEDCs use genetic engineering?
- Prevented by patents and issues of technology transfer.
- Those most in need may not be able to afford it.
- Legal patent = prevents people using something without payment.
What are the issues with patenting and technology transfer?
- Herbicide resistant, pesticide producing soya beans only allowed to grow, use and sell in year seeds were bought.
- spoke about in Supreme Court.
What is “pharming” and what is the issue?
- Adding/removing genes.
- creating human proteins - human genes inserted into a fertilised egg (cow/pig/sheep) -> promotor sequence could mean gene is only expressed in mammary glands - milk contains required human proteins.
- Creating animal models add/remove genes - animals develop diseases.
