BiotechnologyChapter 11

Manipulating DNA1973 Stanley Cohen and Herbert Boyer isolated a gene from DNA of the African clawed frog and then inserted it into the

DNA of E.coli bacteria. During transcription, the bacteria produced frog

rRNA and became the first genetically altered organisms.

Genetic Engineering

Process of manipulating genes for practical purposes.

Process in which biologists make changes in the DNA code of a living organism.

A technology in which the genome of a living cell is modified for medical or industrial use.

Recombinant DNA

Genetic engineering can involve building recombinant DNA.

DNA molecules that are artificially made from two or more different organisms.

Steps in a genetic engineering experiment

Please look over the 4 steps in a genetic engineering experiment on page 229.

Steps in Genetic Engineering

1. Cutting DNA2. Making Recombinant DNA3. Cloning4. Screening

Cutting DNA

DNA from the organism containing the gene of interest is cut by restriction enzymes.

Restriction enzymes are enzymes that destroys foreign DNA molecules by cutting them at specific sites.

Restriction enzymes are bacterial enzymes that recognize and bind to specific short sequences of DNA, and then cut the DNA between specific nucleotides within the sequence.

Cutting DNA continued…

The DNA from a vector is also cut.

Vector – is an agent that is used to carry the gene of interest into another cell.

› Commonly used vectors include: Viruses Yeast Plasmids – from bacterial cellsPlasmid are circular DNA molecules that can replicate

independently of the main chromosomes of bacteria

Making Recombinant DNA

The DNA fragments from the organism containing the gene of interest are combined with the DNA fragments from the vector.

The host cells then take up the recombinant DNA.

Cloning

Gene Cloning – many copies of the gene of interest are made each time the host cell reproduces

Remember that bacteria reproduce asexually by binary fission so it produces identically offspring.

Screening

Cells that received the particular gene of interest are distinguished, or separated, from the cells that did not take up the gene of interest.

The cells can transcribe and translate the gene of interest to make the protein coded for in the gene.

Techniques for genetic engineering

Gel electrophoresis

RFLP Analysis

PCR – Polymerase Chain Reaction

Gel electrophoresis Technique that uses an electric field within

a gel to separate DNA molecules by their size.

DNA fragments are placed at one end of a porous gel and an electric voltage is applied to the gel.

How Gel electrophoresis Works

Restriction enzymes cut DNA into fragments The DNA fragments are poured into wells on a gel.

How it works continued…

The electric voltage is applied to the gel.

The smaller the DNA fragment, the faster and farther it will move across the gel.

How it works continued…

PCR Polymerase Chain

Reaction The polymerase chain

reaction (PCR) is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a DNA .

PCR A method of making many copies

of a piece of DNA

PCR

Large amounts of DNA can be made from a small starting sample

RFLP AnalaysisRestriction Fragment Length

Polymorphism Restriction fragment length

polymorphism or RFLP analysis is used to identify a change in the genetic sequence that occurs at a site where a restriction enzyme cuts.

RFLPs can be used to trace inheritance patterns, identify specific mutations, and for other molecular genetic techniques. 

Applications of genetic engineering

Forensics

Applications of genetic engineering

Gene therapy:the insertion, alteration, or removal of genes within an individual's cells and biological tissues to treat disease.

Applications of genetic engineering

VaccinesThrough the recombinant-DNA procedure, it is now possible to transfer the genes that stimulate antibody formation to a harmless microorganism and use it as a vaccine against the particular disease. Vaccines have been successfully created using the harmless cowpox virus, the herpes simplex type I virus (cold sores), the influenza virus, and the hepatitis B virus through gene splicing.

Applications of genetic engineering

Genetically Modified Crops

Applications of genetic engineering

Cloning

A clone is a member of a population of genetically identical cells produced from a single cell.

In 1997, Ian Wilmut cloned a sheep called Dolly.

Cloning Dolly

Applications of genetic engineering

Transgenic Organisms An organism described as transgenic,

contains genes from other species.

Transgenic Microorganisms

Transgenic bacteria produce important substances useful for health and industry. Transgenic bacteria have been used to produce: insulingrowth hormoneclotting factor

Transgenic Plants 

Transgenic plants are now an important part of our food supply.

Many of these plants contain a gene that produces a natural insecticide, so plants don’t have to be sprayed with pesticides.

Transgenic Animals

Transgenic animals have been used to study genes and to improve the food supply.

Mice have been produced with human genes that make their immune systems act similarly to those of humans. This allows scientists to study the effects of diseases on the human immune system.

Researchers are trying to produce transgenic chickens that will be resistant to the bacterial infections that can cause food poisoning.