Presentation on theme: "DNA Technology In laboratory experiments"— Presentation transcript:
1 DNA Technology In laboratory experiments Genes can be transcribed and translated after being transplanted from one species to anotherCalled “Recombinant DNA” technologyCan be produced via “Genetic Engineering” (laboratory manipulation)
2 Overview: Understanding and Manipulating Genomes One of the greatest achievements of modern science has been the sequencing of the human genome, which was largely completed by 2003DNA sequencing accomplishmentsHave all depended on advances in DNA technology, starting with the invention of methods for making recombinant DNADNA sequencing animation
3 How can we modify a person’s genome? GenomicsHow can we modify a person’s genome?Gene therapy - insertion of genetic material into human cells to treat a disorderEx vivo therapy – cells are removed for a person altered and then returned to the patientIn vivo therapy – a gene is directly inserted into an individual through a vector (e.g. viruses) or directly injected to replace mutated genes or to restore normal controls over gene activityGene therapy has been most successful in treating cancer, to date.
5 DNA CloningConcept 20.1: DNA cloning permits production of multiple copies of a specific gene or other DNA segmentTo work directly with specific genesScientists have developed methods for preparing well-defined, gene-sized pieces of DNA in multiple identical copies, a process called gene cloning
6 24.3 DNA Technology The Cloning of a Gene Cloning: Production of many identical copies of an organism through some asexual means.Gene Cloning: The production of many identical copies of a single geneTwo Ways to Clone a Gene:Recombinant DNAPolymerase Chain Reaction
7 Using Restriction Enzymes to Make Recombinant DNA Bacterial restriction enzymesCut DNA molecules at a limited number of specific DNA sequences, called restriction sites
8 Restriction Enzymes and Sticky Ends Step through animation of cut/splice using EcoRINarrated animation
9 Cloning of a Human Gene / Recombinant DNA Restriction enzymes breaks open a plasmid vector at specific sequence of bases “sticky ends”Foreign DNA that is to be inserted is also cleaved with same restriction enzyme so ends matchForeign DNA is inserted into plasmid DNA and “sticky ends” pair upDNA ligase seals them togetherNarrated animation of “Cloning a Gene”
10 24.3 DNA Technology Polymerase Chain Reaction Amplifies a targeted DNA sequenceRequires DNA polymerase, a set of primers, and a supply of nucleotidesPrimers are single stranded DNA sequences that start replication processAmount of DNA doubles with each replication cycleProcess is now automatedNarrated animationStep by step animation
11 24.3 DNA Technology DNA Fingerprinting Permits identification of individuals and their relativesBased on, polymorphisms differences between sequences in nucleotides between individualsRFLPs : restriction fragment length polymorphismsNarrated animationDetection of the number of repeating segments (called repeats) are present at specific locations in DNADifferent numbers in different peoplePCR amplifies only particular portions of the DNAProcedure is performed at several locations to identify repeats
12 DNA FingerprintsDNA fragments (after digest with restriction enzymes) can be separated throughgel ELECTROPHORESISSee How:AnimationStep-by-step electrophoresisAnother walk-through explanation
13 Forensic EvidenceDNA “fingerprints” obtained by analysis of tissue or body fluids found at crime scenesCan provide definitive evidence that a suspect is guilty or, more specifically, not guiltyIs a specific pattern of bands of RFLP markers on a gelDefendant’sblood (D)Blood fromdefendant’sclothesVictim’sblood (V)DJeansshirtV4 g8 gFigure 20.17
14 DNA fingerprinting Can also be used in establishing paternity Figure: Electrophoresis of PCR-amplified DNA fragments. (1) Father. (2) Child. (3) Mother. The child has inherited some, but not all of the fingerprint of each of its parents, giving it a new, unique fingerprint.
15 24.3 DNA Technology Biotechnology Biotechnology uses natural biological systems to create a product or to achieve a goal desired by humans.“Model Organisms” favored for genetics research
16 Environmental Cleanup Genetic engineering can be used to modify the metabolism of microorganismsSo that they can be used to extract minerals from the environment or degrade various types of potentially toxic waste materials
17 24.3 DNA Technology Transgenic Bacteria Medical Uses: Production of Insulin, Human Growth Hormone, Hepatitis B VaccineAgricultural Uses: Bacteria that protects plants from freezing, bacteria that protect plant roots from insectsEnvironmental: Bacteria that degrade oil (clean up after oil spills), bacteria that remove sulfur from coal
18 Transgenic (GM) Plants 24.3 DNA TechnologyTransgenic (GM) PlantsPlants have been engineered to secrete a toxin that kills insects (ex: Bt corn)Plants have been engineered to be resistant to herbicides (ex: Roundup Ready)Animation: Gene Transfer in Plants Using a Ti Plasmid
19 Agricultural Applications DNA technologyIs being used to improve agricultural productivity and food qualityIn 2008:92% of the soybeans and 80% of the corn planted in the United States had been genetically engineered.
20 Genetic Engineering in Plants Agricultural scientistsHave already endowed a number of crop plants with genes for desirable traitsBt corn (right)
22 Health focus: Ecological concern about GMO crops DNA technologyHealth focus: Ecological concern about GMO cropsResistance increasing in the target pestExchange of genetic material between the transgenic plant and a related speciesConcern about the impact of BT crops on nontarget species (ex: pollinators)
23 GM Animals and “Pharm” Animals Transgenic animalsContain genes from other organismsSometimes called “chimeras”Fig 1. transgenic mouse lines expressing GFP known as “green mice.”
24 24.3 DNA Technology Transgenic Animals Fish, cows, pigs, rabbits and sheep have been engineered to produce human growth hormone in order to increase size of the animals
25 Transgenic organisms have a foreign gene inserted into their DNA Have been engineered to be pharmaceutical “factories”“Pharm” AnimalsFigure 20.18Human breast milk from a cow (2011)
27 “Knockout” miceA number of mice models have been developed: either possessing an inactivated tumor suppressor gene (p53), an activated oncogene (Tg.AC), over-expression of a (human) oncogene (rasH2) or being deficient in nucleotide excision repair (Xpa, de Vries et al., 1995).These mice models have several advantages:the number of animals needed for one study is 120 instead ofthe duration of the study is 6-9 instead of 24 months leading to less distress of the animalsthe transgenic mouse model is considered more discriminating hence improving the accuracy and reliability of human carcinogen identification.
28 Safety and Ethical Questions Raised by DNA Technology The potential benefits of genetic engineeringMust be carefully weighed against the potential hazards of creating products or developing procedures that are harmful to humans or the environmentToday, much public concern about possible hazardsCenters on genetically modified (GMOs) organisms used as food (allergic reactions, etc)Gene “escape”