Biology Exam1 chapter 15

Biology Exam1 chapter 15 - Lecture#22 Chapter 15 Genetic...

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Lecture #22: Chapter 15: Genetic Engineering They needed a way to be able to cut reproducible DNA molecules into pieces Restriction Enzymes: host range restriction enzymes -> the enzymes that break DNA into reproducible pieces -> viruses go into bacteria and reproduces to make viral proteins and then bursts open with all the virus DNA and proteins o Attack incoming DNA and not own DNA used as a defense from bacteriophages in DNA o Used by bacteria as a defense against bacteriophages o Often attack palindromic DNA sequences Palindromic DNA sequences: DIAGRAM: restriction enzyme action DIAGRAM: palindromic DNA sequence For palindromic: its not exact across palindrome: its on the other strand A *A G C T T * is where the cut is going to be made -> bases T T C G A *A not involved -> break covalent bonds DIAGRAM: restriction enzyme If you heat DNA up just a little bit you break the hydrogen bonds (60 degrees C) Each piece of DNA has a single stranded ends -> sticky ends A and A G C T T T T C G A A What can they stick to? Themselves or anything else that has complementary base pairing Restriction enzymes are first part of tool kit We also need a DNA vector -> something able to bring DNA inside the cell so that the cell will use its machinery to make copies of it Vector: anything used as a carrier or means of transfer Recombinant DNA vectors Naturally occurring circular bacteria DNA molecules (plasmids) Bacterial vectors (bacteriophages) Plasmid DNA also in circle but much smaller than cell DNA o It has genes but not any of the genes that bacteria cells need for their normal lives o How does a cell acquire a plasmid? Inheritance If its already in it -> when it prepares to divide by binary fission: it will also replicate the plasmid DNA -> each daughter cell also gets a copy of plasmid DNA Transformation Griffith Bacteria cells without plasmids: incubate them with plasmids on the outside and then the plasmids will go inside the bacteria cells Conjugation Bacteria of two different strains come together and exchange DNA in a sexual process DIAGRAM pg. 325:
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o 1: Millions of identical circular plasmids -> plasmid DNA chose carefully: only one site that can be attacked by restriction enzyme that is being used o Treat plasmid with that enzyme -> o 2. Now have millions of linear plasmids with sticky ends o 3. Have DNA from some other organism (could be human) -> treat that DNA with the same restriction enzyme used on plasmid -> with sticky ends that give complementary
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