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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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Detection of Sickle-Cell

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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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PCR

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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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GMO

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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)

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Gene Therapy

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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Process Animation 15.4Genetic Engineering

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