UA BSC 114 - CH. 20 Notes- BSC 114 (3 pages)

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CH. 20 Notes- BSC 114



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CH. 20 Notes- BSC 114

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Pages:
3
School:
University of Alabama
Course:
Bsc 114 - Principles of Biology I
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CH 20 DNA Tools and Biotechnology The DNA Toolbox o Recently the genome sequences of two extinct species Neanderthals and wooly mammoths have been completed o Advances in sequencing techniques make genome sequencing increasingly faster and less expensive o Biotechnology is the manipulation of organisms or their components to make useful products o The applications of DNA technology affect everything from agriculture to criminal law to medical research o The complementarity of the two DNA strands is the basis for nucleic acid hybridization the base pairing of one strand of nucleic acid to the complementary sequence on another strand o Genetic engineering is the direct manipulation of genes for practical purposes DNA Sequencing o Researchers can exploit the principle of complementary base pairing to determine a gene s complete nucleotide sequence called DNA sequencing o The first automated procedure was based on a technique called dideoxy or chain termination sequencing developed by Sanger o Next generation sequencing techniques use a single template strand that is immobilized and amplified to produce an enormous number of identical fragments Thousands or hundreds of thousands of fragments 400 1 000 nucleotides long are sequenced in parallel This is a type of high throughput technology In third generation sequencing the techniques used are even faster and less expensive than the previous o To work directly with specific genes scientists prepare well defined DNA segments in multiple identical copies by a process called DNA cloning o Plasmids are small circular DNA molecules that replicate separately from the bacterial chromosome o Researchers can insert DNA into plasmids to produce recombinant DNA a molecule with DNA from two different sources o The production of multiple copies of a single gene is a type of DNA cloning called gene cloning o A plasmid used to clone a foreign gene is called a cloning vector Using Restriction Enzymes to Make a Recombinant DNA Plasmid o Bacterial restriction enzymes cut DNA molecules at specific DNA sequences called restriction sites o A restriction enzyme usually makes many cuts yielding restriction fragments o The most useful restriction enzymes cut DNA in a staggered way producing fragments with sticky ends Amplifying DNA o The polymerase chain reaction PCR can produce many copies of a specific target segment of DNA PCR uses a pair of primers specific for the sequence to be amplified PCR amplification occasionally incorporates errors into the amplified strands and so cannot substitute for gene cloning in cells PCR primers can be designed to include restriction sites that allow the product to be cloned into plasmid vectors Determining Gene Function o One way to determine function is to disable the gene and observe the consequences o Using in vitro mutagenesis mutations are introduced into a cloned gene altering or destroying its function o When the mutated gene is returned to the cell the normal gene s function might be determined by examining the mutant s phenotype Gene expression can also be silenced using RNA interference RNAi Synthetic double stranded RNA molecules matching the sequence of a gene is used to break down or block the gene s mRNA Cloning Plants Single Cell Cultures o In plants cells can dedifferentiate and then give rise to all the specialized cell types of the organism o A totipotent cell such as this is one that can generate a complete new organism Plant cloning is used extensively in agriculture Human Gene Therapy o Gene therapy is the alteration of an afflicted individual s genes o Gene therapy holds great potential for treating disorders traceable to a single defective gene o Vectors are used for delivery of genes into specific types of cells for example bone marrow o Gene therapy provokes both technical and ethical questions


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