3.5 GENETIC MODIFICATION OF ORGANISMS
Nature of science:
Assessing risks associated with scientific research—scientists attempt to assess the risks associated with genetically modified crops or livestock. (4.8)
Understandings:
• Gel electrophoresis is used to separate proteins or fragments of DNA according to size.
• PCR can be used to amplify small amounts of DNA.
• DNA profiling involves comparison of DNA.
• Genetic modification is carried out by gene transfer between species.
• Clones are groups of genetically identical organisms, derived from a single original parent cell.
• Many plant species and some animal species have natural methods of cloning.
• Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells.
• Methods have been developed for cloning adult animals using differentiated cells.
• Gel electrophoresis is used to separate proteins or fragments of DNA according to size.
• PCR can be used to amplify small amounts of DNA.
• DNA profiling involves comparison of DNA.
• Genetic modification is carried out by gene transfer between species.
• Clones are groups of genetically identical organisms, derived from a single original parent cell.
• Many plant species and some animal species have natural methods of cloning.
• Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells.
• Methods have been developed for cloning adult animals using differentiated cells.
Exploring DNA
DNA is at the very core of what gives animals and plants their uniqueness. New techniques developed: copying DNA, using DNA to reveal identity, mapping DNA by finding A, T, C or G, cutting and pasting genes to make new organism, and cloning of cells and animals
DNA is at the very core of what gives animals and plants their uniqueness. New techniques developed: copying DNA, using DNA to reveal identity, mapping DNA by finding A, T, C or G, cutting and pasting genes to make new organism, and cloning of cells and animals
dna profiling
DNA profiling is used in:
1. Isolate DNA from biological materials from the crime scene (hair, blood, etc.) and possible suspects 2. Polymerase chain reaction
4. Gel electrophoresis
5. Make single stranded DNA
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Human genome project
- Begun formally in 1990 the international projects aims
- Completed April 2003
- Number and loci of all genes in our genome (30,000). Fewer than expected => complex relationship between genes.
- New proteins and functions discovered. Better drugs design using knowledge of protein structure
- DNA comparisons can be made with other species. Closely related species share more similarities in the DNA sequence. Used to infer evolutionary history
gene transfer
- Universality of genetic code allows genes to be transferred from one organism to the other
- Genes are transferred between species, the amino acid sequence of polypetides translated from them is unchanged
Plasmids = vector = medium by which genes of interest are transferred to host
small (2 - 30 genes) loops of bacterial DNA
A host cell (bacterium):
receives a gene of interest
via a vector replicates repeatedly, passing on gene of interest to offspring
Restriction enzymes
produced naturally by bacteria as defense against viruses
- used to cut the desired section of the DNA
- recognizes unique sequences of DNA in plasmid and in gene of interest
- Cuts complementary sticky ends in gene of interest and plasmid
- allow incorporation of gene of interest into plasmids
- creates covalent bonds
- joining together gene of interest within plasmid,
- producing recombinant DNA
GMO = genetically modified organism
BT corn
Genes from Bt have been inserted into maize so GM plants can produce an insecticidal toxin and therefore be resistant to pests, e.g. European Corn Borer.
Potential Benefits:
Bt corn risk to monarch butterflies
Potential Benefits:
- Introduction of a new trait – Bt gene increases resistance to pests such as the European Corn Borer
- Results in increased productivity – less land used / greater yield / less crop damage
- Less use of chemical pesticides – reduced cost / ecological damage to wild the economic cost of farming
- Increased disease resistance
- Less use of chemical herbicides
- Less use of chemical fetiliser
- Increased hardiness – better drought/cold slinity tolerance and therefore can be grown in more locations / has a longer growing season
- Increased nutritional content
- Could be toxic to or cause allergic reactions in humans
- Transferred genes could mutate after testing
- Non-target organisms affected by toxins
- Increases resistance to toxin evolves in pests
- Accidental release may result in competition with native plant species
- Super weeds - through cross-breeding the introduced gene could be transferred to wild varieties
- Biodiversity reduced – both plant populations by direct competition and animal populations directly and indirectly could be affected
- Patent laws prevent farmers producing locally suitable varieties – this would lead to unregulated field tests, not a desirable situation
Bt corn risk to monarch butterflies
- The caterpillar stage of the Monarch feeds on milkweed.
- Milkweed commonly grows on the edge of corn fields
- Studies show some mortality in Monarch caterpillars fed milkweed leaves covered with Bt corn pollen
gene patenting
- Patent = Intellectual property right
- Right to prevent others from making, using selling patented product without permission
cloning
- Clone = group of genetically identical organisms or group of cells derived from single parent
- Cloning for medical purposes
- Cloning animal models of disease: create multiple copies of transgenic organism with disease causing mutation in genes
- “Pharming” for drug production
- Farm animals such as cows, sheep and goats are genetically engineered to produce drugs or proteins
- Cloning stem cells for research
- Retrieving endangered or extinct species
- Cloning dinosaurs?
- Need well preserved DNA
- Reproducing a deceased pet
- Cloning humans?
- Couples that can’t have child
- Couples that have lost child
gel electrophogenesis
This laboratory technique is used to separate fragments of DNA in an effort to identify its origin. Enzymes are sued to chop up the long filaments of DNA into varying sizes of fragments. The DNA fragments are placed into small wells in the gel, which are aligned along one end. The gel is exposed to an electric current, positive on one side and negative on the other.
• Application: Use of DNA profiling in paternity and forensic investigations.
• Application: Gene transfer to bacteria using plasmids makes use of restriction endonucleases and DNA ligase.
• Application: Assessment of the potential risks and benefits associated with genetic modification of crops.
• Application: Production of cloned embryos produced by somatic-cell nuclear transfer.
• Skill: Design of an experiment to assess one factor affecting the rooting of stem-cuttings.
• Skill: Analysis of examples of DNA profiles.
• Skill: Analysis of data on risks to monarch butterflies of Bt crops.
Theory of knowledge:
•The use of DNA for securing convictions in legal cases is well established, yet even universally accepted theories are overturned in the light of new evidence in science. What criteria are necessary for assessing the reliability of evidence?
• Application: Gene transfer to bacteria using plasmids makes use of restriction endonucleases and DNA ligase.
• Application: Assessment of the potential risks and benefits associated with genetic modification of crops.
• Application: Production of cloned embryos produced by somatic-cell nuclear transfer.
• Skill: Design of an experiment to assess one factor affecting the rooting of stem-cuttings.
• Skill: Analysis of examples of DNA profiles.
• Skill: Analysis of data on risks to monarch butterflies of Bt crops.
Theory of knowledge:
•The use of DNA for securing convictions in legal cases is well established, yet even universally accepted theories are overturned in the light of new evidence in science. What criteria are necessary for assessing the reliability of evidence?