Chap_19 - Chapter 19 Chapter 19 Recombinant DNA Recombinant...

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Unformatted text preview: Chapter 19 Chapter 19 Recombinant DNA Recombinant DNA Technology Technology Basic Concepts The first recombinant DNA experiments were done in 1973 Stanley Cohen (Stanford U.) and Herbert Boyer (UCSF) made the first recombinant DNA molecule Combined DNA from two different sources to create a new DNA molecule Recombinant DNA Technology Techniques for manipulating DNA Recombinant means DNA from different sources is combined to create a novel DNA molecule Also use the general term of genetic engineering Impact of Recombinant DNA Milestone in biological studies Prior to recombinant DNA technology, scientists had to: Infer the genotype from the phenotype Mutations were limited to inducing random mutations Biotechnology Recombinant DNA that developed in university research labs naturally led to the development of commercial products Drugs Hormones Genetically engineered food crops Working at the Molecular Level Genetic studies at the molecular level present formidable challenges How do you identify the gene of interest? Suppose YFG ( y our f avorite g ene) is 3,300 bp in the human genome The human genome is ~3.3 billion (3.3 X 10 9 bp) YFG is 1/1,000,000 th (10-6 ) of the genome Once you locate YFG, how do you produce enough of the DNA in a form pure enough for biochemical studies? What if you want to make the protein encoded by YFG? As we have discussed, there are significant differences in DNA replication, transcription and translation between bacteria and human cells? Proper expression of a human gene in a bacterial cells presents yet another set of challenges Cutting and Joining DNA Fragments Fundamental requirement for DNA manipulation Possible by the discovery of a group of bacterial enzymes called restriction endonucleases Commonly called restriction enzymes Restriction Enzymes Make double-stranded cuts in DNA Bacterial defense against viruses Degrade foreign DNA Why isnt the bacterial genome degraded? Bacterial DNA is marked by DNA methylation to prevent degradation by its own restriction enzymes Three Types of Restriction Enzymes Type I Recognize a specific DNA sequence, but cut the DNA at a distance ~1,000 bp away Not useful for recombinant DNA Type II Recognize a specific DNA sequence and cut the DNA within that sequence These are the enzymes used for molecular cloning Type III Very recently found Similar to Type I, but the DNA is cut about 25 bp from the recognition sequence Found after a number of bacterial genomes had been sequenced Restriction Enzymes More than 800 different enzymes that recognize more than 100 different DNA sequences have been identified Some enzymes recognize the same DNA sequence The most commonly used enzymes are commercially available Common Features of Restriction Enzymes The first part of the name identifies the bacterial species from which it was...
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Chap_19 - Chapter 19 Chapter 19 Recombinant DNA Recombinant...

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