Presentation on theme: "Chapter 15 – Genetic Engineering"— Presentation transcript:
1 Chapter 15 – Genetic Engineering HOW AND WHY DO SCIENTISTS MANIPULATE DNA IN LIVING CELLS?
2 SOME REASONS WHY:Increase the yield from plants and animals (milk, beef, chicken, corn, soybeans, etc)Disease and pest prevention/resistanceCloningMedical ResearchGene TherapyGenetic TestingPersonal identification (DNA fingerprint)
3 15.1 Selective Breeding Selective Breeding Taking advantage of naturally occurring genetic variations to pass wanted traits to the next generation.Methods used to selectively breed:Hybridization – crossing dissimilar individuals to bring together desirable characteristics from eachEx. (disease resistance X food producing capacity)2. Inbreeding – breeding individuals with similar characteristics to ensure unique traits are preserved (pure bred dogs)
4 15.2 Recombinant DNA (Finding Genes) Can we change the DNA of a living cell?Cut the DNA using restriction enzymesBuild a DNA sequence with the gene or genes desiredEnzymes like ligase connect the sticky ends of two DNA pieces togetherRecombinant DNA – joining DNAfrom two or more different sources
5 Plasmids and Genetic Markers Problem: DNA molecules insertedinto host cells were not replicated:Solution: Use plasmids to introducePlasmid – a piece of circular bacterial DNAPlasmids generally contain:a. a replication start signal (ori),restriction enzyme start site (EcoR1)genetic markers like antibiotic resistance genes (tetracycline and ampicillin)
6 Plasmids and Genetic Markers Recombination Process using PlasmidsThe same restriction enzyme is used to cut plasmid and DNA of interestThe DNA of interest is joined to the plasmid using ligaseRecombined DNA is inserted into the host cellThe genetic marker (like antibiotic resistance) identifies the recombined DNA after bacterial growth
8 Plasmids and Genetic Markers Use for recombined genes:Human growth hormone (HGH), insulin, gene therapy, resistance of crops to pests and herbicides, pollution control, designer species
9 Transgenic OrganismsTransgenic – organisms that contain genes from other species, produced by insertion of recombinant DNA into the genome of a host organismUsed in plants, animals and microorganisms – increased our understanding of gene regulationGenetically modified plants
10 Transgenic OrganismsTransgenic Plants – transformed by using bacteria such as Agrobacterium, removing the cell wall or directly injectedTransgenic Animals – transformed by injecting DNA directly into the nucleus of egg cells.In each case the goal is to have thehost cell combine the recombinantDNA with it’s own chromosomes
11 CloningClone – A member of a population of genetically identical cells produced from a single cellSteps in nuclear transplantation cloning:Nucleus of an unfertilized egg is removedEgg cell is fused with a donor cell that contains a nucleusThe egg and donor cell are fused using an electric shockDiploid egg develops into an embryoEmbryo is implanted in the uterine wall of a foster mother.Animals cloned: frogs, sheep (Dolly 1997), cows, pigs, mice and cats
12 15.3 Applications of Genetic Engineering Have you eaten genetically modified (GM) foods this week?GM Crops – transgenic plants that resist pests, herbicides, disease and result in increased yields.-Use of these crops is on the rise-Introduced in 1996 (soybean)-As of 2014 GM crops made up 94% of soybeans, 96 % of cotton and 93% of cornExamples: Roundup ready soybeans, Bt corn, tomatoes, rice, potatoes and stacked varieties (HT and Bt traits) BT Corn Video
13 15.3 Applications of Genetic Engineering GM animals – engineered to increaseproduction, nutritional benefit orproduct not typically associated withthat animal.30% of milk in US is coming fromcows injected with bovine growthhormone (BGH)In 2008, US approved the sale ofmeat and milk from cloned animals.
14 15.3 Applications of Genetic Engineering Examples of GM foods:Cows – rBGH, increased milk outputPigs – leaner meat, omega 3 acidsSalmon – GH, shorter time to marketAquabounty - SalmonGoats – spider genes to manufacture silk, antibacterial goat milk
15 Gene TherapyGene Therapy – an absent or faulty gene is replaced by a normal, working gene.The first attempted of a gene transfer to cure a disease occurred in 1990.Scientist engineer a virus to carry the new gene into the target cellsProblem: need reliable ways to insert working genes in target cells and ensure DNA used does no harm.
16 DNA FingerprintingRestriction enzymes are used to cut the DNA into fragments containing genes and repeatsThe restriction fragments are separated according to size using gel electrophoresisThe DNA fragments containing repeats are then labeled using radioactive probes. This labeling produces a series of bands – the DNA fingerprint.