Recombinant DNA and Genetic EngineeringChapter 13

Selective Breeding (Ch. 13.1)

Remember… Selective

breeding is used to produce plants and animals with desired traits.

Genetic Engineering (Ch. 13.2)

Genes are isolated, modified, and inserted into an organism

Made possible by recombinant technology

Cut DNA up and recombine pieces

Amplify modified pieces

What do you think about eating genetically modified foods?

Genetically modified organisms are called transgenic organisms.

TRANSGENIC ANIMALS

1. Mice – used to study human immune system

2. Chickens – more resistant to infections

3. Cows – increase milk supply and leaner meat

4. Goats, sheep and pigs – produce human

proteins in their milk

Transgenic Goat

Human DNA in a goat cell

This goat contains a human gene that codes for a blood clotting agent. The blood clotting agent can be harvested in the goat’s milk.

Restriction Enzymes

Molecular scissors that cut DNA at a specific nucleotide sequence

Over 200 different restriction enzymes are known, each isolated from bacteria and able to cut DNA in a unique manner

Scientists use restriction enzymes in the process of genetic engineering.

Restriction enzymes

Recombinant DNA

The ability to combine the DNA of one organism with the DNA of another organism.

Recombinant DNA Technology

“Cutting and Pasting”

Enzymes: Restriction

enzymes = “cut”

Ligase = “paste”

Therefore, a recombinant DNA molecule contains different regions from different sources

DNA (Gene) cloning

Want to study or isolate a particular gene Need to get many copies (amplification) of the

gene so it can be studied adequately Most organisms only have one or two copies of

any gene per cell, so we need a way to amplify copies of that gene

Do that via cloning into a vector This allows scientists to make additional copies

of the gene using bacteria

Using Plasmids

Plasmid is small circle of bacterial DNA

Foreign DNA can be inserted into

plasmid

Forms recombinant plasmids

Plasmid is a cloning vector

Can deliver DNA into another cell

Using Plasmids

Polymerase Chain Reaction (PCR)

PCR allows scientists to make many copies of a piece of DNA.

1. Heat the DNA so it “unzips”.

2. Add the complementary nitrogenous bases.

3. Allow DNA to cool so the complementary strands can “zip” together.

Polymerase Chain Reaction

Double-stranded DNA to copy

DNA heated to 90°– 94°C

Primers added to base-pair with ends

Mixture cooled; base-pairing of primers and ends of DNA strands

DNA polymerasesassemble new DNA strands

Figure 16.6Page 256

Stepped Art

Polymerase Chain Reaction

Figure 16.6Page 256

Stepped Art

Mixture heated again; makes all DNA fragments unwind

Mixture cooled; base-pairing between primers and ends of single DNA strands

DNA polymerase action again doubles number of identical DNA fragments

Gel Electrophoresis

DNA is placed at one end of a gel A current is applied to the gel DNA molecules are negatively charged

and move toward positive end of gel Smaller molecules move faster than larger

ones Function- to separate DNA fragments

Gel Electrophoresis

What are these techniques used for? Forensic: identifying criminals & victims Identifying disease genes in animals &

humans Gene Therapy: inserting of new working

copies of genes into humans Animal knockouts: turning off of a specific

gene in order to discover its function

DNA Fingerprinting

Engineered Proteins

Bacteria can be used to grow medically

valuable proteins

Insulin, interferon, blood-clotting factors

Vaccines

Engineered Plants

Cotton plants that display resistance to herbicide

Aspen plants that produce less lignin and more cellulose

Tobacco plants that produce human proteins Mustard plant cells that produce

biodegradable plastic

Cloning Dolly

1997 - A sheep cloned from an adult cell

Nucleus from mammary gland cell was

inserted into enucleated egg

Embryo implanted into surrogate mother

Sheep is genetic replica of animal from

which mammary cell was taken

The Human Genome Initiative

Goal – Sequence all human DNA Initially thought by many to be a waste of

resources Sequencing was mostly completed ahead

of schedule in early 2001

Ethical Issues

Who decides what should be

“corrected” through genetic

engineering?

Should animals be modified to provide

organs for human transplants?

Should humans be cloned?