3.5 Genetic modification and biotechnology Flashcards
What is genetic engineering?
Genetic engineering is the direct human manipulation of an organism’s genome. It involves the introduction of foreign DNA into an organism or altering or deleting an existing gene.
- Once engineered the DNA is considered to be recombinant, the organism is known as a Genetically Modified Organism (GMO)
PCR
Polymerase Chain Reaction
- Used to amplify a small sample of DNA
- Used in forensic science
- Big limitation: any contamination will ruin the whole process
- Stages:
- Temperature is increased to separate strands (denaturation)
- Temperature is decreaed to allow primers to base pair complementary to DNA strand (annealing)
- Heat-resistant Taq polymerase replicates DNA to build new strand (elongation)
Gel electrophoresis
A technique used to separate proteins or fragments of DNA according to size
- Samples are placed in a block of gel (semi-solid medium)
- An ellectric current is applied, which causes the samples to more through the gel (remember: the phosphate group in DNA’s backbone causes it to be negatively charger overall)
- DNA and RNA molecules have a negative electrical charge and will move towards the positive electrode in an electric field
- Smaller proteins or DNA strands will move fast with less resistance and so move farther through the gel while larger molecules on the other hand move slower and travel less distance
- This results in samples of different sizes to travel at different speeds and end up at different distances, creating bands in the gel
Used to identify DNA –> foresnic science
Restriction endonucleases
Enzyme
Used to cut DNA into fragments to isolate the desired DNA fragment
These enzymes cleave (cut) the backbone of the DNA double helix at highley specific sequences
Sticky ends: when the enzyme cuts DNA and leaves unpaired bases
DNA profiling
- Comparison of DNA
- Used in foresnic science and to determine family relationships
- It usually involves a combination of PCR, Restriction Enzymes, Gel Electrophoresis )and Sothern Blotting?)
People who are more related with each other will share a similar DNA profile, noted by multiple matching bands within an electrophoresis gel.
Genetic modification
The process of changing an organisms genome by transferring genes from one species to another.
- Because the genetic code is universal, an organism can express a new trait if the appropriate gene is introduced into its genome.
Stages in gene transfer
- Isolation - isolating the genes (example: a human gene + a plasmid)
- Restriction - using restriction endonuclease enzyme cutting the human dna section and plasmid section
- Ligation - sticking the DNA backbones of the gene (from the human cell) to the plasmid plasmid using the ezyme ligase
- Transformation - transfer the plasmid with the target DNA (called a recombinant plasmid) back into a bacterium.
- Selection - choose that bacteria that has been transformed
- Culturing - grow large quantitues of it
Insulin gene being genetically modified into a bacterial cells genome
- Isolation - mRNA extracted from human pancreatic cells is treated with reverse transcriptase to make complementary DNA
- Restriction - an appropriate plasmid is isolated and cut with a restriction enzyme
- Ligation - the plasmid and DNA are fused using the enzyme DNA ligase
- Transformation - he recombinant plasmid is introdiced into bacterial host cells
- Selection - these bacteria that have been transformed are selected
- Culturing - they are grown in large quantities to produce insulin. The human insulin is then separated and purified so that it can be used by patients.
Bt corn
Genetic modification of crops
- Scientists have genetically modified corn so that it produces a poison which kills harmful insects
- The farmer no longer needs incesticides
- The insect killing gene comes from the bacteria Bacilus thuringiensis
Advantages: - The environment is no longer exposer to large amounts of incesticide
- The farmer no longer has to walk around a drum of toxic spray waring a mask and protective clothing
Disadvantages: - Bt corn will poisin insects over a long period of time (unlike incesticides which the farmer would spray once or twicce) this means the insect can become accustomed (resistant) to the poison.
- A variety of insects are at risk of being killed it might be harmgul ones or beautiful ones like butterflies (Monarch butterflies).
Clones
Genatically identical organisms derived from a single original parent cell
- Organisms that reproduce asexually produce offspring that are genetically identical to the parent. Asexual reproduction is a natural way of producing clones.
- Also binary fission in prokaryotes
- Additionally, mechanisms exist whereby sexually reproducing organisms can produce clones (e.g. identical twins)
What does cloning multicellular organisms require?
The production of stem cells.
- Stem cells can be artificially generated from adult tissue using a process called somatic cell nuclear transfer (SCNT)
Somatic cell nuclear transfer
Method to clone adult animals using differentiated cells
Somatic cell nuclear transfer is a method by which cloned embryos can be produced using differentiated adult cells
1. Donor somatic cells are taken from the organism that will be cultured and cloned
2. An unfertilised egg is taken from another donor
3. The nucleus is removed from the unfertilised egg
4. The nucleus from the somatic cell is transferred into the donor to make a diploid egg cell.
5. An electric current is then delivered to stimulate the egg to divide and develop into an embryo
6. The embryo is transplanted into the uterus of the surrogate mother
7. The pregnancy and birth of the offspring proceed as normal.
Example: Dolly the sheep
Cloning via splitting or fragmentation of an embryo
Involves artificially splitting a developed embryo into multiple parts and implanting them into surrogates which will take them to term, making identical clones of the original embryo.
- The early stage of an embryo (eight cells of the morula) is composed of cells that are totipotent stem cells (potential to develop into any type of tissue)
- It is possible to split an eight-cell embryo into eight individual cells and implant each of these cells into surrogate mothers.
- These ‘split’ embryos would then develop into eight clones of the original zygote and form normal organisms.
- This can happen spontaneously as well; monozygotic, or identical, twins in humans are born when a very early embryo breaks apart and each part develops independently.
Risks associated with genetic modification of crops
- Crops may limit the biodiversity of the local environment
- New traits cam cause unexpected health problems - allergic reactions
- Unintended resistance in weeds because of cross pollination
- Patents restrict farmers from accessing GM seeds (biotech companies hold monopolies over crop use)
Benefits associated with genetic modification of crops
- Pest-resistant crops
- Improved nutritional value
- Resistance to high temperatures
- Longer shelf lives for GM foods - genes which slow the rate of spoiling
- Increase food supply in poor countries (improved yields)
