Component 2.7 - Recombinant DNA technology Flashcards
How do you obtain a double stranded piece of DNA using reverse transcriptase?
1) MRNA coding for a gene is obtained from a human cell
2) Reverse transcriptase produces a single strand of complementary DNA
3) DNA polymerase is used to build a double strand of cDNA
How do you insert DNA into a plasmid?
1) Plasmid removed from bacterial cell and gene is identified from human DNA
2) Restriction enzymes are used to cut open plasmid and the same ones are using to cut out the gene in the human DNA
3) Ligase, DNA fragments, plasmids mixed together and the ligase attaches human gene to plasmid at sticky ends
Why is reverse transcriptase better than restriction endonucleases?
1) Restriction endonucleases could cut gene into non-functional fragments.
2) Introns are not present so removes the need for post-transcriptional processing to produce functional mRNA
3) Do not have to locate gene
How are genetic markers used?
Bacterial cells are cultured in growth medium containing the antibiotic.
If they have incorporated the plasmid they also contain the gene for antibiotic resistance
Pros of genetic engineering
1) Medical products
2) Can introduce specific traits which can enhance crop growth
Cons of genetic engineering
1) Plasmids are easily transferred - plasmids containing antibiotic resistance gene can exchange genetic material with other bacteria and it could possibly transfer to a pathogenic species
2) Human cells may contain oncogenes - these could activate oncogenes in recipient cells
3) Micro organisms with new gene could be released into environment and be a threat
Arguments in favour of GM crops
1) High crop yield (insect/fungus resistance)
2) Pesticide reduction (genes for pathogen resistance)
3) Superior keeping qualities
Arguments against the use of GM crops
1) Dispersal of pollen from crops to wild relatives (could create super weeds)
2) Reduction in biodiversity
3) Unknown effect of eating new protein produced in crop
What are the two types of gene therapy?
Somatic cells - targets body cells in the affected tissue but changes are not inherited
Germ-line therapy - introduces corrective genes into the picture so the genetic correction is inherited (very rare)
What is gene therapy?
A technique in which a defective allele is replaced with one cloned from a healthy individual
What is tissue engineering?
Using methods of biochemistry, cell biology, engineering and material science to repair improve or replace biological functions
What are stem cells?
An undifferentiated cell capable of dividing to give rise to daughter cells, which can develop into different types of specialised cell or remain as undifferentiated stem cells
Examples of stem cells
Embryonic stem cells: Blastocyst contains ESCs which can form every cell type in the body
Some adult tissues: bone marrow, muscle and brain contain adult stem cells and they can replace cells that are lost through wear, tear and disease but cannot form any cell type
Ethical issues with obtaining stem cells from embryos, cloning human tissues and organs
1) Researchers can create embryos for research and people argue life should not be made as a means to an end
2) Moral status of embryo. Some agree life begins at conception and others believe it is when it acquires a nervous system
3) Some believe it is not justified as adult stem cells could be used
4) Some people fear that stem cells may lead to humans being cloned
Duchenne Muscular Dystrophy cause and effect?
Cause: Recessive sex linked allele
Effect: Mutation if dystrophin gene, meaning a failure to produce dystrophin (important structural component of muscle tissue). This means severe wasting of muscle
