UNIT 3.5 Flashcards
(28 cards)
Gel Electrophoresis
Gel electrophoresis: a laboratory technique used to separate and isolate proteins or DNA fragments based on mass/size
1) Enzymes cut DNA into different-sized fragments
2) The DNA sample is placed at one end of the porous gel
3) This side of the gel with the DNA sample is exposed to a negative electrical current and moves towards the positive side
4) The DNA fragments move through the gel and stop at different points, creating a band, they move through the gel based on their charge
5) Smaller fragments move further through pores in the gel
6) The bands are dyed so we can see them
Gel Electrophoresis: Two factors determine the movement of DNA through the electrophoresis gel
*Check Good Notes for Diagram
Charge: Since DNA is negatively charged the negative electrical charge repels the negative DNA towards the positive end
Size: The smallest fragment will be the furthest away from the origin while larger fragments get stuck up top
DNA Profiling
Process:
*Check Good Notes for Diagram
DNA profiling: a technique where individuals can be identified and compared via their DNA profiles
Overview of the process:
1. The DNA sample is collected (eg: blood, semen, saliva)
2. Amplified using PCR using Taq DNA polymerase
3. Satellite DNA - long stretches (with STR sequences) are cut with specific restriction enzymes to generate fragments
4. Fragments are separated using gel electrophoresis and the resulting profiles are compared
DNA Profiling: Forensic Investigations
*Check Good Notes for Diagram
Suspects should match completely with the DNA sample taken
DNA Profiling: Paternity Testing
*Check Good Notes for Diagram
A parent should match half of the child’s
Genetic Modification (GMO)
GMO: carried out by gene transfer between species since genetic code is universal and still translates the same polypeptide
*The gene determines a particular trait by encoding for a specific polypeptide-given organism
*As genetic code is an almost universal organism and expresses new trailer if the appropriate gene is introduced into its genome
GMO: transfer of genes between species
Transfer: new organism created
Other genetic modifying examples:
- Spider spunk
- GM plants (reversal)
- A pig with the modified gene of
*The genetic information came from skin cells from Turkish Angora female cats
*Inserted into pigs making red fluorescent protein
Benefits & Risks of Potential Risks Associated with GMOs: Environmental
Benefits:
*Pest-resistant crops: Less chemical insecticides are used
*Less need to spray insecticides/pesticides: Save fuel and Reduce carbon footprint
*Improved shelf-life: means less wasted/spoiled food in stores
Risks:
*Toxins in pest-resistant GMOs could negatively impact: non-target organisms and harm ecosystems
*Cross-species pollination could spread herbicide-resistance genes: Creating ‘superweeds’
*Biodiversity could be negatively affected by: the destruction of pests, Weeds, and even competing plants
Benefits of Potential Risks Associated with GMO: Health
Benefits:
*Nutritional value of foods can be improved by: enhancing vitamins
*Crops can be produced that
lack: natural allergens, toxins
*GM crops can be engineered to produce: Cheap, Edible, Vaccines
*GM bacteria produce cheap medical compounds such as insulin and clotting factor
Risks:
*Proteins from transferred genes could be toxic or cause allergic reactions
*Antibiotic resistance genes used as markers during gene transfer could spread to pathogenic bacteria
*Transferred genes could:
mutate cause, unexpected risks
Benefits of Potential Risks Associated with GMO: Agriculture
Benefits:
*Crops can be made be resistant to:
Drought, Cold, Salinity
Expanding
range for farming
Increasing crop yields
*Herbicide-resistant GM crops allow
easy killing of weeds that sap nutrients from crop plants
*Crop varieties can be produced that are resistant to viruses
Risks:
*GMOs with pest toxins could increase the evolution of resistance in certain pest populations
*Big biotech companies hold
monopolistic legal rights (patents) over GM seeds: farmers must pay large sums for seeds each year.
*They are not permitted to save and re-sow seeds, so strains are not able to adapt to local conditions.
Data Analysis: Effect on BT crops on Monarch Butterflies
Farmers would protect crops from pests by spraying with chemical pesticides.
Today, many crops are genetically modified with a gene from the
Concerns have been raised that the spread of Bt corn may also be impacting the survival rates of monarch butterflies.
*Monarch butterflies feed on milkweed which often grows near Bt crops.
*When pollen from the BT crops ends up dusting milkweed plants, butterflies consume the toxin and die
Bacterium Bacillus turingiensis (BT Corn)
Bacterium Bacillus turingiensis (BT corn): is a genetically modified maize that incorporates producing a gene
It is lethal to certain types of larvae
Kills targeted pests like the corn-borer worm
Kills non-target insects
1999 Study Investigating Association between exposure to BT corn pollen and Survival rates of Monarch Butterflies
Some Scientist say Lack of Validity:
*Check Good Notes for Diagram
1) Monarch caterpillars were fed milkweed leaves that had been dusted with pollen from Bt corn (to simulate spread via wind)
2) Growth and mortality rates were compared against caterpillars fed on non-dusted leaves or leaves dusted with non-GM pollen
3) Caterpillars exposed to Bt pollen were found to have eaten less, grew more slowly and exhibited higher mortality rates
Lack of validity as they do not accurately reflect natural conditions:
* There were higher amounts of Bt pollen on the leaves than would be found naturally (e.g. rain would diminish build-up)
*Larva were restricted in their diet (in the field, larvae could feasibly avoid eating pollen-dusted leaves)
populations
Second Study About Effect of BT Crops on Monarch Butterflies
Comparing the survival rates of monarch butterflies based on proximity to Bt corn fields:
*There was no significant increase in mortality when monarch larvae were placed in or near an actual Bt cornfield
RESULT: From this, it was concluded that exposure to Bt pollen poses no significant risk to monarch butterfly
Gene Transfer Insulin
Insulin is a hormone (protein) secreted by the pancreas to regulate the glucose level in blood, it tells the liver to store excess glucose as glycogen
Since genetic code is universal, it will always code for the same polypeptide
Gene Transfer Insulin:
1. Isolating Gene and Vecto
Method Used:
Function:
Vector:
Method used: PCR
Function: DNA is isolated from cells by centrifugation where heavier components such as nuclei are separated → The gene of interest is amplified
Vector: a DNA molecule that is used as a vehicle to carry the gene of interest into a foreign cell
eg: bacterial plasmids - since they are capable of autonomous self-replication and expression
Gene Transfer Insulin:
2. Digestion with Restriction Enzymes
Enzyme Used:
Function:
Enzyme used: Restriction enzymes
Function: “cut” the desired gene from
the genome → leaves 2 sticky ends → cut into the plasmid
Gene Transfer Insulin:
3. Ligitaion of Vector and Insert
Enzyme Used:
*Check Good Notes for Diagram
Enzyme: Ligase
1) The gene of interest is inserted into a plasmid vector that has been cut with the same restriction enzyme
2) this occurs because the sticky ends of the gene and vector are complementary base pairing
3)DNA ligase connects to form a recombinant construct, by fusing their sugar-phosphate backbones together with a covalent phosphodiester bond
Gene Transfer Insulin:
4. Selection and Expression - Isolation of Transgenic Cells via Antibiotic Resistance
*Check Good Notes for Diagram
The recombinant contrast is introduced into an appropriate host cell
Antibiotic selection is used to identify which cells have successfully incorporated
The plasmid vector contains an antibiotic resistance gene so only transgenic cells will grown
Clone
Clones: A group of genetically-identical organisms
*Derived from a single original parent cell
*Organisms that reproduce asexually always produce genetically identical offspring (clones)
*Clones are rarer in sexually reproducing organisms (i.e. monozygotic twins)
*A clone can be very large, such as in the case of commercially grown potatoes, but it can always be traced back to an original parent cell.
Somatic Cell Nuclear Transfer
*Check Good Notes for Diagram
Cloning multicellular organisms requires the production of stem cells (differentiated cells cannot form other cell types)
Stem cells can be artificially generated from adult tissue using a process called somatic cell nuclear transfer (SCNT)
Overview - Nuclear transfer:
- Somatic cells are removed from the adult donor and cultured (these cells are diploid and contain the entire genome)
- An unfertilised egg is removed from a female adult and its haploid nucleus is removed to produce an enucleated egg cell
- The enucleated egg cell is fused with the nucleus from the adult donor to make a diploid egg cell (with the donor’s DNA)
- An electric current is then delivered to stimulate the egg to divide and develop into an embryo
- This embryo is then implanted into the uterus of a surrogate and will develop into a genetic clone of the adult donor
Natural Cloning
Binary Fission:
Budding:
Fragmentation:
Parthenogenesis:
Plant Cloning Methods
Human Cloning Methods
*Check Good Notes for Diagram
Binary Fission: Parent organisms divide equally in 2 so produce two identical daughter organisms eg: Planaria (flatworms), bacteria and protists
Budding: Cells split off the parent organism, generating a smaller daughter organism which eventually separates from the parent eg: Hydra
Fragmentation: New organisms grow from a separated fragment of the parent organisms eg”: starfish and annelid worms
Parthenogenesis: Embryos are formed from unfertilized ova (via the production of a diploid egg cell by the female) eg: insects, finish, amphibians and reptiles
Plant Cloning Methods:
*Plants have the capacity for vegetative propagation
*Adult plants possess meristematic tissue capable of cellular differentiation (totipotent)
* Algae can be produced asexually by spores
Human Cloning Methods:
*Identical twins are created when a zygote splits into 2 identical cells, each forming an embryo
*Non-identical twins are when an unfertilized egg splits into two cells and each is fertilized by a different sperm
Artificial Cloning
*At the early stage, embryonic cells are pluripotent (they can divide into any type of tissue)
*If these cells are separated artificially in a laboratory, each group of cells will form a cloned organisms
*The separated groups of cells are then implanted into the uterus of a surrogate to develop into genetically identical clones
Therapeutic Cloning: Arguments in Favour
Embryonic cells can be induced to differentiate to create specific tissues or organs for transplantation
- Stem cells can be created without the need for fertilization and destruction of ¨natural human¨ embryos
- Source of cells for stem cell transplants, such as leukaemia, diabetes, burn and many other medical cases
- Transplants do not require the death of another human
- Transplants are less likely to be rejected as they are cells which are genetically identical to the patient
- Embryos are not allowed to develop to the point where a nervous system forms, so there is no pain or perception
