section17_ak - MIT Department of Biology 7.014 Introductory...

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MIT Department of Biology 7.014 Introductory Biology, Spring 2005 Recitation Section 17 Answer Key April 11-12, 2005 Recombinant DNA and Cloning A. The Tools Recombinant DNA is a set of tools that allows scientists to move between genetics, biochemistry and molecular biology – allowing us to determine how the parts of a cell or organism work. 1. What does it mean to clone a gene? Cloning DNA means to isolate a gene or fragment of DNA away from the other DNA of an organism and be able to propagate this piece. 2. What is a vector? Vectors (or plasmids) are naturally occurring small pieces of circular DNA that can replicate in various organisms. In this course we concentrate on plasmids, which are designed to propagate in microorganisms. 3. What do the restriction enzymes do? How are they physically able to perform this function? Restriction enzymes (naturally occurring in bacteria) make it possible to cut DNA at predetermined sequences without damaging the DNA sequence. All interactions in biology are based on shape and chemical identities of the interacting surfaces. Restriction enzymes recognize particular sequences in DNA by making physical contact with the portions of the bases exposed in the grooves of the DNA molecule. Once properly positioned over the recognition site, the enzyme is able to perform a symmetric cut. 4. What is a library? A library is a set of vectors containing DNA inserts that collectively represent all of the DNA in a genome or all of RNAs expressed in a cell. Each vector has only one piece of DNA or cDNA, but collectively the vectors contain all of the information. 5. What three features must vectors or plasmids have? Why? Plasmids and vectors have origins of replication that allows for replication in organisms. A plasmid or a vector has a restriction site recognized by a restriction enzyme, where a piece of
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section17_ak - MIT Department of Biology 7.014 Introductory...

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