3.5 – Genetic Modification & Biotechnology

Essential Idea: Biologists have developed techniques for artificial manipulation of DNA, cells and organisms. 3.5 Genetic Modification and Biotechnology 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 Gene 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 Applications: Use of DNA profiling in paternity and forensics investigations Gene transfer to bacteria using plasmids makes use of restriction endonucleases and DNA ligase Assessment of the potential risks and benefits associated with genetic modification of crops Productions of cloned embryos produced by somatic-cell nuclear transfer Skills: Design an experiment to assess one factor affecting the rooting of stem-cuttings Analyze examples of DNA profiles Analyze data on risks to monarch butterflies of Bt crops

Review the steps of DNA Replication WITH A PARTNER: Review the steps of DNA Replication

PCR – Polymerase Chain Reaction For other techniques, substantial quantities of DNA are necessary PCR is used to make millions of copies of a DNA sample so that other biotechnologies can be done https://www.youtube.com/watch?v=x5yPkxCLads

template DNA (DNA to be copied) Requirements template DNA (DNA to be copied) a thermostable form of the DNA polymerase III enzyme from a thermophilic bacteria (Taq polymerase) Primers free-floating nucleotides (deoxynucleoside triphosphates – dNTPs) http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter18/polymerase_chain_reaction.html https://www.youtube.com/watch?v=x5yPkxCLads

II. Gel Electrophoresis -Used to separate fragments of DNA

A. Restriction enzymes (endonucleases) are used A. Restriction enzymes (endonucleases) are used to cut up DNA into fragments of varying sizes -Cut DNA at specific sites (restriction sites) – usually palindromes -Found naturally in bacteria – used to cut up invading viral DNA -Once DNA is cut, results in restriction fragments with sticky ends

B. Fragments placed in holes at one end of a slab of charged gel

C. DNA fragments move through gel towards positive pole D C. DNA fragments move through gel towards positive pole D. Smaller pieces of DNA move farther faster than larger pieces creating a banded pattern Discuss as a table: WHY do DNA fragments move towards the positive pole? WHY do smaller pieces move farther and faster than larger ones?

DNA Profiling/Fingerprinting A. Match an unknown sample of DNA with a known sample B. If patterns are the same = same person Patterns similar = probably related https://www.youtube.com/watch?v=ZAuWYP7rt0A

C. Often use non-coding sections of DNA the include STRs (short tandem repeats)

D. Used for paternity testing, criminal D. Used for paternity testing, criminal investigations, determining evolutionary and ecological relationships

V. Gene Transfer A. AKA gene modification or gene cloning – take a gene out of one organism and place it into a different organism 1. Used to create cold- and pest-resistant crops B. REMEMBER – Universal Genetic Code

Discuss as a table: What might be some of the downsides of this type of technology?

C. Steps of Gene Cloning Gene of interest identified and isolated (ex.insulin) -Also need a cloning vector which will carry the gene – most often a bacterial plasmid

2. Gene of interest and vector are cut with the same restriction enzymes, resulting in complimentary sticky ends

3. The target DNA is fused into the plasmid using DNA ligase 4. The vector carrying the gene of interest is introduced into bacterial cells by transformation

5. Select for cells that have been transformed – usually gene of interest is linked to gene for antibiotic resistance and then the bacteria is grown on plates containing antibiotics – only the cells that have taken up the new plasmid grow

Cloning A. Many plants and some animals have natural methods of cloning

B. Reproductive cloning - Making copies of whole organisms

C. Therapeutic cloning - Making copies of embryonic/adult stem cells (AKA stem cell research) 1. Its aim is to develop cells which have not yet gone through the process of differentiation

Ethical Issues surrounding therapeutic cloning a. Therapeutic cloning starts with production of human embryos - Is it ethically acceptable to generate a new human embryo for the sole purpose of medical research? b. In nature, embryos are created only for reproduction and many people believe that using them for experiments is unnatural and wrong c. Embryonic stem cells has led to major breakthroughs in human biology d. Scientists are coming closer and closer to growing skin to repair serious burns, growing new heart muscle to repair an ailing heart, growing new kidney tissue to rebuild a failing kidney e. With rare exceptions, the vast majority of researchers are against the idea of reproductive cloning in humans

DISCUSS AS A TABLE While showing utmost respect for different and opposing views, discuss the pros and cons of therapeutic cloning. Share your own opinions if you wish, but be polite!