BTY100-Lec#5.1 Genetic Engineering © LPU : BTY100

Outline Introduction to Genetic Engineering Goal Tools Process Molecular Scissors Cloning Vectors Process Enhanced Traits- Bt Crops © LPU : BTY100

Genetic Engineering Goal Altering/ Manipulating the traits of living organisms by changing the information encoded in their DNA. Goal To add one or more new traits that are not naturally already found in that organism.  © LPU : BTY100

Altering DNA? Is it possible? DNA is a ‘universal language’. The genetic code means the same thing in all organisms. All living organisms have the same bases (A, T, G, C) which code for proteins. The codons they form always code for the same amino acids, so transferred DNA codes for the same polypeptide chain in the host organism as it did in the donor organism. © LPU : BTY100

Human appearance is a results of the information stored in our genes Human appearance is a results of the information stored in our genes. Differences in Eye color, hair color, skin complexion, height etc all are due to different information stored in different persons. Does it means any change in our DNA will result in some change in our appearance? © LPU : BTY100

Changing faces of Michael Jackson….????? A Question for you….? In one of the most memorable moments of Oprah's interview, Michael told her he had a skin disorder that destroyed the pigmentation of his skin. The disease, called vitiligo, was in his family, Michael said. "It is something I cannot help”. Genetic Engineering? OR Skin Bleaching? OR Skin Disease??? He kept getting whiter and whiter and whiter, and nobody understood why © LPU : BTY100

Coming back to our Question Does it means any change in our DNA will result in some change in our appearance? Answer- NO, The Purpose of science is not this……. Ultimate aim of all type of researches is to benefit the society. In this unit we will be discussing the examples which were created for some useful purpose. © LPU : BTY100

How does Genetic Engineering work? removing a gene from one organism and inserting it into another (a process called gene transfer). When a gene for a desirable trait is taken from one organism and inserted into another, it gives the ‘recipient’ organism the ability to express that same trait. © LPU : BTY100

Glossary Donor cell- is the cell that provides the new DNA fragment for the recipient cell Recipient cell/Host Cell- is the cell that is reviewing the ‘new’ DNA. Target Gene/Foreign DNA- Gene with the desired trait. Ligation- Uniting attaching two DNA fragments. DNA recombination- The DNA fragment to be cloned is inserted into a vector. Transformation- The recombinant DNA enters into the host cell and proliferates © LPU : BTY100

GENETIC ENGINEERING: PROCESS © LPU : BTY100

PROCESS: © LPU : BTY100

Tools for Genetic Engineering Molecular Scissors Construct/Cloning Vectors © LPU : BTY100

Molecular Scissors Restriction enzymes are DNA-cutting enzymes found in bacteria. A restriction endonuclease : cuts DNA at or near a particular place known as restriction sites. E.g. EcoRI: always cuts at site: GAATTC © LPU : BTY100

Cloning Vectors A DNA molecule that: carries foreign DNA into a host cell. replicates inside cell and produces many copies of itself and the foreign DNA. E.g.: Plasmid: an extrachromosomal circular DNA molecule that replicates on its own inside the bacterial cell © LPU : BTY100

Transformation The plasmids carrying the desired traits are introduced into host cells via a process called transformation. Bacteria are most commonly used as host cells for gene cloning because : Their DNA can be easily isolated and reintroduced into their cells. Bacterial cultures also grow quickly, rapidly replicating the foreign genes. Bacteria will also produce large amounts of the protein of interest © LPU : BTY100

Process… Gene of interest is cut out with Restriction enzyme. Host plasmid is cut with same Restriction enzyme. Gene is inserted into plasmid and ligated with ligase enzyme New plasmid inserted into bacterium (transform). Bacteria divides and plasmid divides along with that. © LPU : BTY100

Genetic Engineering: Enhanced Traits © LPU : BTY100

Bt Crops Are crops that are genetically engineered to produce the same toxin as produced by B. thuringiensis in every cell of the plant, with the goal of protecting the crop from pests. Examples: Bt Cotton, Bt corn, Bt Brinjal What is Bt? Bacillus thuringiensis (Bt) is a spore forming bacterium that produces crystals protein (cry proteins), which are toxic to many species of insects © LPU : BTY100

Bt Cotton Bt Cotton is a variety of cotton that has been genetically engineered to produce an insecticide in every cell. It contains the gene coding for Bt toxin, causing cotton plant to produce this natural insecticide in its tissues. In many regions, the main pests in commercial cotton are lepidopteran larvae, which are killed by the Bt protein in the transgenic cotton they eat. This eliminates the need to use large amounts of broad-spectrum insecticides to kill lepidopteran pests © LPU : BTY100

How Bt Works? When insects attack and eat the cotton plant the Cry toxins are dissolved. This is made possible due to the high pH level of the insects stomach. The now dissolved and activated Cry molecules bind to cells in the insect gut and results in the death of epithelial cells. The death of such cells creates pores in the insect gut and insect dies eventually. © LPU : BTY100

Why Bt is not toxic to Humans? The specificity of Bt rests on the fact: For the activation of toxin, alkaline conditions are required as provided by insect gut but the human stomach has a pH of  1.5 to 3.5. The toxicity of the Bt protein is receptor-mediated. This means that for an insect to be affected by the Bt protein, it must have specific receptor sites in its gut where the proteins can bind. Humans do not have these receptors. Before Bt crops are placed on the market, they must pass very stringent regulatory tests, including those for toxicity and allergenicity. © LPU : BTY100

Advantages Reduced environmental impacts from pesticides Increased opportunity for beneficial insects Reduced pesticide exposure to farm workers and non-target organisms © LPU : BTY100

Risks Invasiveness – Genetic modifications can potentially change the organism to become invasive. Resistance to Bt - The biggest potential risk to using Bt-crops is resistance. Farmers have taken many steps to help prevent resistance. Cross-contamination of genes - Although unproven, genes from GM crops can potentially introduce the new genes to native species. © LPU : BTY100

Next Class: Genetic Engineering:A Potential Solution © LPU : BTY100