1. Recombinant DNA and Genetic Engineering
Chapter 13

3. Selective Breeding (Ch. 13.1)
Remember…
Selective breeding is used to produce plants and animals with desired traits.

4. 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

6. What do you think about eating genetically modified foods?

7. Genetically modified organisms are called transgenic organisms.
TRANSGENIC ANIMALS
Mice – used to study human immune system
Chickens – more resistant to infections
Cows – increase milk supply and leaner meat
4. Goats, sheep and pigs – produce human proteins in their milk

8. Transgenic Goat
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.
Human DNA in a goat cell

9. 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.

10. Restriction enzymes

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

12. Recombinant DNA Technology
“Cutting and Pasting”
Enzymes:
Restriction enzymes = “cut”
Ligase = “paste”

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

14. 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

15. 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

16. Using Plasmids

17. Polymerase Chain Reaction (PCR)
PCR allows scientists to make many copies of a piece of DNA.
Heat the DNA so it “unzips”.
2. Add the complementary nitrogenous bases.
3. Allow DNA to cool so the complementary strands can “zip” together.

18. Polymerase Chain Reaction
Double-stranded
DNA to copy
Polymerase Chain Reaction
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 polymerases
assemble new
DNA strands
Stepped Art
Figure 16.6 Page 256

19. Polymerase Chain Reaction
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
Stepped Art
Figure 16.6 Page 256

20. 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

21. Gel Electrophoresis

22. 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

23. DNA Fingerprinting

24. Engineered Proteins
Bacteria can be used to grow medically valuable proteins
Insulin, interferon, blood-clotting factors
Vaccines

25. 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

26. 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

27. 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

28. 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?