Genetic

Engineering

MILLER-LEVINE BIOLOGY BOOK

PAGES 247-259

BREEDING TECHNIQUES

Selective Breeding:

Description: The oldest and most obvious way of improving species Select a few individuals to serve as parents for the next generation Cross individuals with a desired trait

Example(s): Luther Burbank produced 250 new varieties of fruit in addition to the daisy and Burbank Potato

Inbreeding:

Description:• Technique used to maintain a stock of similar organisms Individuals with similar characteristics are crossed so the traits will appear again in next generationPROBLEM: Increased risk of recessive genetic defects.

Example(s): Purebred dogs

Hybridization:

Description: A cross between dissimilar individuals of

different, but related species Offspring are often hardier than either parent

Example(s): Commercially grown corn

Mutagens:

Description:A breeder might not want to wait for a beneficial mutation to appear naturally. They catalyze this!Mutagens include radiation and chemicals. They cause mutations• With luck and time, breeders end up with “good” mutants

Example(s): Useful bacterial strains. Some bacteria can digest oil are are useful in cleaning up oil spills.

GENETIC ENGINEERING

ARTIFICIALLY ALTERING GENETIC MAKE-UP, OFTEN USING DNA FROM ONE ORGANISM IN ANOTHER

STEP 1: ISOLATE THE DESIRED GENE

Restriction Enzymes:Proteins that cut DNA sequences at specific regions• More than 75 are known• Each one recognizes a specific site of 4-6 nucleotide pairs and cuts• Make it possible to cut DNA into fragment that can be isolated, separated and analyzed

STEP 2: COMBINE THE GENE(S) WITH DNA FROM RECIPIENT ORGANISM

DNA Recombination:Insert desired gene into organism--often bacterial plasmid (small circular pieces of bacterial DNA)• DNA now consists of parts from different kinds of organisms• This is “recombinant DNA”

STEP 3: INSERT COMBINED DNA INTO NEW ORGANISM

DNA Insertion:It is easiest to transfer DNA into bacterial cells• Mix plasmids in with millions of bacteria in a salt solution• Altered plasmids will carry foreign DNA into bacterial cells• Bacteria are isolated and grown into large colonies to magnify the amount of the gene (DNA cloning)• Using different techniques, recombinant DNA can be inserted into yeast cells, animals and plants

GENETIC SCREENING

DETERMINING THE NUCLEOTIDES ON DNA, USING GEL ELECROPHORESIS

READ NEW SEQUENCES OF DNA

DNA Sequencing:• Only one strand is used in DNA sequencing• Many copies of the strand are needed and produced via DNA cloning• Add radioactive phosphorus to DNA• Divide DNA into 4 groups that undergo different chemical treatments that break DNA into pieces• DNA pieces are separated by gel electrophoresis and banding patterns are analyzed to reveal sequence of bases

TRANSGENIC ORGANISMS

ORGANISMS THAT CONTAIN FOREIGN

GENES

BACTERIA:

Description:• Organisms that contain foreign genes are transgenic• When a gene coding for a human protein is inserted into bacteria, the recombinant cells may produce large amounts of the protein

Example(s): Human growth hormone, Insulin to treat diabetes, Interferon to block growth of viruses and treat cancer

PLANTS:

Description:• DNA can be injected into plant cells directly or attached to plasmids of certain species of bacteria that infect plant cells

Example(s):

• The goal is to produce plants that manufacture natural insecticides and fertilizer

• Firefly gene inserted into tobacco plant and it glowed!

ANIMALS:

Description:• DNA can be introduced into reproductive cells by injection, among other techniques

Example(s):

• Scientists introduced growth hormone gene from rainbow trout into carp. The new fish were bigger and faster growing.

• Another goal is to produce farm animals that are resistant to disease.

CLONING

The production of genetically identical organisms from single cells

CLONED ANIMALS:

Description:• The nucleus of an egg cell is removed and replaced with a nucleus taken from an adult organism• The egg is grown inside a foster mother• The newborn is a genetic copy of the adult from which the nucleus was takenExample(s):

• In 1997 “Dolly” the sheep was cloned. Cows and mice have been cloned as well.

GENE THERAPY:

Transgenic Humans

Genetic Engineering to treat disease

Description:• Transgenic humans can be produced by inserting foreign genes into human cells• Remove cells from an individual and grow them in culture. Transform with a corrective gene and reinsert• Viruses can be modified so they cannot cause disease

GENETIC ENGINEERING IN HUMANS:

Example(s):

• Cystic fibrosis, Tay-Sachs disease and sickle-cell anemia are examples of genetic disorders that could be treated in this manner

Now that you have some scientific background you can make and support your arguments.

Are you FOR or AGAINST GENETIC ENGINEERING?

Legislative Analyst - presents the necessary scientific background required to understand the genetic engineering application and the proposition – the law that is being proposed. Paper and presentation should include:

Description of propositionExplanation of SCIENCE background relevant to

propositionProponent - presents the argument in favor of the proposition and the science supporting the proposition. Paper and presentation should include:

Position (YES on proposition)Explanation of SCIENCE in support of propositionRelevant ethical issues related to proposition

Opponent - presents the rebuttal to the argument in favor of the proposition and the science against the proposition.

Paper and presentation should include:Position (NO on proposition)

Explanation of SCIENCE against of propositionRelevant ethical issues related to proposition