Genetic modification and biotechnology Flashcards
1
Q
What is PCR and how does it work?
A
- Polymerase chain reaction (PCR), replicate large quantities of DNA from a small initial sample
Check steps in book
2
Q
How much DNA is doubled with every cycle of PCR?
A
- Using equation 2^n
- n= number of cycles
- E.g. initial = 10ng
10 x 2^5 = 320ng
3
Q
What is Gel electrophoresis used for?
A
- Separates and isolates proteins or DNA fragments based on mass or size, used after PCR
- DNA samples placed in a block of gel, electric current passed through, since DNA is negatively charged, move towards cathode +
- Smaller pieces move faster through the gel, causes samples of different sizes to separate
4
Q
What is satellite DNA?
A
- Short DNA sequences, number of repeats vary between individuals
- They can be divided into fragments by restriction enzymes
- Used in DNA profiling
- They include short tandem repeats (STR)
5
Q
What is DNA profiling? What are STRs?
A
- Individuals can be identified and compared via their respective DNA profiles
- The short tandem repeats (STRs) are used which are non-coding regions that make up long stretches of DNA
- Individuals will have different number of repeats at a specific DNA locus
6
Q
How is DNA profiling used in paternity and forensic investigations?
A
- DNA sample collected and amplified using PCR
- Satellite DNA (including STR sequences) are cut with restriction enzymes to generate fragments
- Fragment length will differ between individuals since the STR also vary in length
- Fragments separated using gel electrophoresis and resulting profiles compared
7
Q
How is DNA profiling used in forensic investigations and how in paternity testing?
A
- Forensic: Suspects DNA matched with DNA evidence found at crime scene for a conviction to occur
- Paternity: Since children inherit half their chromosomes from each parent, have comparable DNA with mother and father
8
Q
Be able to analyse examples of DNA profiles.
A
9
Q
What is gene modification?
A
- Transfer of genes between species, new organism called transgenic
- Possible since humans have a common ancestor, genetic code is the same between species, universal
10
Q
What are the four main steps for genes transfer to occur in bacteria?
A
- Isolation of gene and vector by PCR
- Digestion of gene and vector by restriction endonuclease
- Joining of gene and vector by DNA ligase
- Selection and expression of transgenic construct
11
Q
Explain step 1 of gene transfer.
A
- DNA isolated from cells, heavy components separated
- Gene of interest is amplified by PCR
- A vector is a DNA molecule that is used as a vehicle to carry the gene of interest into a foreign cell
- Example of vector: bacterial plasmids, since they can self-replicate or viruses/artificial chromosomes
12
Q
Explain step 2 of gene transfer.
A
- The vector (plasmid) and gene of interest are cut with restriction enzymes at recognition sites to put the gene into the plasmid
- Restriction enzyme used: restriction endonucleases, generates sticky ends
- Either sticky ends or blunt ends
13
Q
Explain step 3 of gene transfer.
A
- Gene of interest is inserted into a plasmid vector that was cut with the same restriction endonucleases
- This happens because the sticky ends of the gene and vector overlap (complementary base pairing)
- Enzyme DNA ligase link gene and vector together to form a recombinant construct, they form covalent bonds
14
Q
Explain step 4 of gene transfer.
A
- The recombinant construct (plasmid) is inserted into a bacterial cell
- The cell will grow and reproduce
- Antibiotic selection is then used to identify which cells have successfully incorporated the recombinant construct
15
Q
What happens in antibiotic selection?
A
- To show it the plasmid is correctly incorporated, and if the gene is expressed
- If the bacteria is resistant, it will grow in the solution of antibiotics
- The transgenic cells (cell in which the DNA is inserted into), once isolated and purified will begin expressing the desired trait encoded by the gene
Check book
16
Q
What are genetically modified organisms (GMOs) used for?
A
- In agriculture they improve crop yield to reduce farming costs
17
Q
What are three advantages of genetic modified organisms?
A
- New positive traits introduced, any desired trait can be developed, adaptation to the current conditions and demands. E.g Golden corn, increase Vitamin A content (prevent blindness)
- Provide greater yield, bring about economic advantages, greater profit and lower prices for consumers.
- Higher yield means less land is needed, more natural ecosystems, less pesticide need to be sprayed
18
Q
What are four risks of genetic modified organisms?
A
- Modified species may out-compete native species or kill non-pest species, reduction of biodiversity
- Not all nations and farmers have access to the technology, increased pest attacks, increased inequality between farms
- Exposure to new genes could cause unknown impacts and damage to human health, allergic reactions
- Crops with pest toxin could accelerate the evolution of resistant pest species
19
Q
What is Bt corn and how does it put monarch butterflies at risk?
A
- Genetically modified maize that incorporates an insecticide producing gene from the bacterium Bacillus thuringiensis
- Insecticide is lethal to the corn larvae (before butterfly)
- Spread of the Bt (protein) corn cay impact survival rates of monarch butterflies
- Pollen of Bt also contain Bt toxin, spread to milkweed which is main source of food for monarch butterfly
20
Q
What study was done on Bt corn and monarch butterflies? What did the scientists change?
A
- 1999 preliminary study, suggested in a laboratory setting monarch caterpillars were more likely to die when feeding on milkweed plants that was dusted with pollen of Bt corn, higher mortality rates
- 2001, believed risk to monarchs from Bt toxin was minimal, no significant increase in mortality when placed in corn field
- Other reasons for mortality, climate change
21
Q
What are clones?
A
- Groups of genetically identical organisms or group of cells derived from a single original parent cell
- Asexual reproduction, genetically identical clones (sexually reproducing also with identical twins)
- Requires the production of stem cells
22
Q
What are the two methods of cloning?
A
- Splitting of an embryo to clone an animal before the cells have differentiated (natural)
- Somatic cell nuclear transfer (artificial)
23
Q
What is somatic cell nuclear transfer and how does it produce cloned embryos?
A
- Donor somatic body cells taken from the organism and cultured in the lab (cells are diploid)
- An unfertilized egg is taken from another individual and enucleated (nucleus removed)
- The enucleated egg cell is fused with the nucleus from the adult donor to make a diploid egg cell (with the donor’s DNA)
- Electric current is delivered to stimulate the egg to divide and develop into an embryo
- Embryo implanted into the uterus of a surrogate and will develop into a genetic clone of the adult donor
24
Q
What is the natural method of cloning?
A
- In animals the early stage of an embryo is composed of totipotent stem cells (can differentiate into any or all types of tissues)
- Embryos can be split, each fraction can be implanted into surrogate mothers. These split embryos can develop into clones of the original zygote and form normal organisms (identical twins)
- The offspring will retain the same features regardless of the characteristics of the surrogate mother, not genetically related
25
For what is the method of using differentiated cells used?
- Reproductive cloning: the embryo is implanted into the uterus of a surrogate, a new cloned organism will develop
- Therapeutic cloning: embryonic cells can be induced to differentiate to create specific tissues or organs for transplantation (bone marrow)
26
What are 4 methods of natural cloning in animals?
- Binary fission: chromosome copied and cell split in half, 2 cells with a copy of the chromosome e.g. flatworms
- Budding: cells split off the parent, generates a smaller daughter organism, separates from the parent e.g. yeast
- Fragmentation: new organisms grow from a separated fragment of the parent organism e.g. starfish
- Parthenogenesis: embryos are formed from unfertilized ova e.g. fish
27
What are 2 natural methods of cloning in plants?
- Tubers can form new plants which are genetically identical to parent plant
- Garlic and onion bulbs are modified plant leaves, genetically identical
28
What factors affect rooting of stem-cuttings?
- Allowing a stem cutting to root by putting it in water can produce a clone. Large number can be generated
Factors:
- Internal: position of cutting, age of starring plant, surface area of leaves on stem cutting
- External: length & intensity of light exposure, temperature off cutting, concentration of rooting hormones
29
How to design an experiment on factors affecting stem cutting?
- 1 Independent variable, select a range
- 1 Dependent variable, how you are going to measure it
- Research question
- Method, focus on controlled variables and repeat trials
- Collect and process data, how you will do this
- Include JUSTIFICATIONS
