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AP Biology: Chapter 14 DNA Technologies
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Recombinant DNA methods
Restriction enzymes Enzymes from bacteria Used to cut DNA molecules in specific places Enable researchers to cut DNA into manageable segments Vector molecule Carrier of DNA fragment into cell Plasmids Engineered viruses Transformation Uptake of foreign DNA into cells
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Splicing Foreign DNA into a Vector
Foreign DNA and plasmid DNA cut with same restriction enzyme Produces linear molecules with complementary single-stranded ends Recombinant DNA created by mixing so sticky ends pair DNA ligase forms covalent bonds, linking the two fragments Plasmid Vector Video
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Genetic probes Segments of single-stranded DNA that can hybridize to complementary base sequences in target gene Southern blot technique
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Genomic library Chromosome library cDNA library
Collection of DNA fragments that represent all the DNA in the genome Chromosome library All the DNA fragments in that specific chromosome cDNA library Produced using reverse transcriptase Makes DNA copies of modified mRNA
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Amplifying DNA in vitro by PCR
Small amount of double-stranded DNA DNA precursors Specific nucleic acid primers Taq DNA polymerase DNA is denatured Primers attach to primer-binding site on each DNA strand Each strand acts as template for DNA synthesis
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DNA sequencing Based on chain termination method
Yields information about Structure of gene Probable amino acid sequences of its encoded proteins
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Comprehension Check The gel at the right was produced from four samples of single-stranded DNA fragments that were incubated with radioactively labeled primer, DNA polymerase, the four nucleotides, and a different one of the four dideoxy nucleotides. 1. What is the sequence of nucleotides shown in this gel? ________________ 2. What is the sequence of nucleotides in the original single-stranded DNA fragment? _________________ GACTGAAGCTGTT CTGACTTCGACAA
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Applications of DNA technology
Gene therapy Tissue engineering DNA typing
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Transgenic organisms Have a gene from some other organism inserted into their genome Gene targeting Adds precision to transgenic technology “Knocks out” or “knocks in” gene of interest at particular chromosomal locus, where it trades places with an existing gene. By causing a specific gene to be inactive in the mouse, and observing any differences from normal behavior or condition, researchers can infer its probable function Mouse on right is normal; mouse on left is transgenic animal expressing rat growth hormone
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Safety guidelines Safety concerns Safety measures
Introduction of transgenic organisms into the environment Health effects on humans from consuming genetically modified crops Safety measures Special facilities designed to hold pathogenic organisms Science of risk assessment: the benefits must outweigh the possible hazards
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