© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 1
Manipulation of DNA
Selective breeding has manipulated DNA f/ eons Domesticated animals demonstrate the power of it Some dogs differ dramatically from their wolf ancestors
Molecular approaches now possible Give greater power, precision and speed We can change one gene & transfer it Transfer between species
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Restriction Enzymes
Cut DNA at highly specific pointsFour to seven basesEach enzyme is unique
Consistent results
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Other Enzymes
LigaseJoins DNA fragments together
DNA PolymeraseMakes copies of DNA of interest from a
template
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Gel Electrophoresis
Separation of DNA fragments
Based on size
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DNA Hybridization
Radioactive DNA probe Binds only to complimentary DNA template
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DNA Cloning
Makes many identical copies of a geneNecessary for certain operations:Sequencing, gene transfer, hybridization
DNA is obtained by screening a DNA library (a collection of different DNA pieces)
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Screening a DNA Library
One DNA is isolated from the many The library is in bacteria which are plated on
agar Form colonies Each colony has one gene
Screen by DNA hybridization DNA probe for gene of interest Isolate one colony and amplify it
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Polymerase Chain Reaction (PCR)
Rapid cloning by polymerase amplification Cycles through 3 temperatures
High – meltingLow – annealing of primersMedium – polymerase extension
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DNA Fingerprinting
Identifies individuals & is used in:Forensics casesPaternity cases
RFLP analysis PCR amplification
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RFLP
DNA cut with Restriction Enzyme
Gel electrophoresis DNA hybridization Compare bands
between suspects D V and see if match crime scene DNA
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Genetic Engineering
Transferring genes between organismsGenetically Modified Organism (GMO)
Plasmids, viruses, or gene guns Changes the phenotype
Faster growth Insect, herbicide, disease, or frost resistanceLonger shelf-life
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Human Cloning Therapeutic Cloning
Produces transplant tissues
Reproductive cloning Produces identical
offspring (a clone)
First Gene Therapy PatientAshanthi DeSilva
1. Born w/o a properly functioning immune system
2. ADA (adenosine deaminase deficiency)
Types of Gene therapy
1. Gene therapy currently only genetically engineers somatic cells
The correction is not inherited & has to be performed every few months.
Gene therapy that integrated into DNA did not have to be repeated, but caused cancer
2. Genetic engineering can also be done in germline, which will be inherited
Genetic engineering of germline
Genetic engineering of people has begun!
Parents will be able to make offspring at will!
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Ethical Issues
Where should the limits be drawn?Bioengineering of bacteria, plants, dogs,
humans?Pesticide resistance – more pesticide use?Bovine Growth Hormone – necessary?Human cloning – therapeutic, reproductive?Gene therapy – human bioengineering?
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Concept Quiz
What is an advantage of restriction enzymes?
A. They cut DNA into manageable-sized pieces.
B. They cut at a specific sequence and, therefore, give consistent results.
C. They leave sticky ends which can be used in cloning.
D. All of the above
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The purpose of a DNA library is to
A. Store DNA
B. Isolate specific genes
C. Access DNA sequence information
D. Genetically modify E. coli
Concept Quiz
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RFLP analysis
A. Is one method of DNA fingerprinting.
B. Provides 100% accurate positive results.
C. Is used in diagnosis of human diseases.
D. All of the above.
Concept Quiz
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Process Animation 15.1Genetic Testing: Identifying the Sickle-Cell Allele
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Process Animation 15.2Constructing a DNA Library
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Process Animation 15.3aHuman Cloning: Therapeutic Cloning
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Process Animation 15.3bHuman Cloning: Reproductive Cloning
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