1. Bellwork: What do humans commonly use selective breeding for
Bellwork: What do humans commonly use selective breeding for? Are there any issues associated with it’s use?

2. In today’s class We will look at different forms of selective breeding
Advantages and disadvantages
How scientists make and combine DNA fragments
How scientists incorporate DNA into other organisms
Transgenic plants and animals
Cloning

3. Selective Breeding
Section 15.1

4. What is selective breeding?
Selective breeding takes advantage of naturally occurring genetic variation, to pass wanted traits on to the next generation of organisms

5. Selective breeding doesn’t just apply to animals….
Corn lost the ability to survive in the wild but gained many valuable agricultural traits
Hard case around kernels for example disappeared

6. Hybridization
The crossing of dissimilar individuals together to bring together the best of both organisms
Hybrids (the offspring of these crosses) are often hardier than their parents
American Botanist Luther Burbank was a pioneer of hybridization in the late 1800s
Combined properties such as disease resistance and fruit productivity

7. Inbreeding
Inbreeding is the continued breeding of individuals with similar characteristics
Why you have pedigree dogs
Dog show winners can be very valuable
Animals can be used as stud animals
Often successful racehorses or award winning cattle

8. How do you counteract some of the problems associated with selected breeding?
The wide variation found in natural populations of species makes selective breeding possible
Genetic variation can be increased by breeders by incorporating mutations, which are a source of biological diversity
When scientists manipulate the genetic make up of an organism they are using biotechnology
Biotechnology is the application of a technological process, invention or method to living organisms
Selective breeding is a form of biotechnology

9. Bacterial mutations
Breeders can affect the mutation rate by using radiation or chemicals
Many mutations can be harmful
Others can be very beneficial
Produce useful characteristics not usually found in the population
This technique works very well with bacteria
As they are so small, millions can be ‘treated’ at the same time
Allowed scientists to produce useful strains of bacteria
Bacteria for cleaning up oil spills
Scientists working on bacteria to clean up radiation or metal pollution

10. Polyploid plants
When chromosome do not separate properly during meiosis
In plants – can produce many useful characteristics
Polyploidy is fatal in animals
In plants, produces many traits that breeders want to utilize

11. Summary
Selective breeding is widely utilized to reinforce certain characteristics of animals and plants
Explains dog breeds
Explains why we have cultivated crops different to wild varieties
Hybridization - the crossing of individuals with contrasting characteristics
Inbreeding – the reinforcing of characteristics within a population
Bacterial mutations – have the potential to be very useful in society
Polpyploid plants are often utilized by breeders to incorporate useful traits into a gene pool

12. Recombinant DNA
Section 15.2

13. Copying DNA of living organisms
Until recently breeders could only work with variations that occur in nature
Now it is possible to go a step further, and certain genes can be transferred between organisms
Finding specific genes on the DNA molecule is hard
Like finding a needle in a haystack
Solution – magnet
Similar approach to working with DNA

14. Finding the genes
Douglas Prasher in 1987 wanted to identify the genes in jellyfish that make them glow green (the gene that codes for Green Fluorescent Protein (GFP))
He thought the GFP could be linked to when the protein was being made in the cell
Like attaching a lightbulb to that molecule
Prasher studied the amino acid sequence of the protein
Using a genetic code table he predicted the mRNA base sequence
He then used a complimentary base sequence to attract an mRNA that matched his predictions
He then checked, and found that this mRNA occurred naturally in jellyfish
He then found the gene, by taking a gel with restriction fragments of jellyfish DNA
One fragment bound to the mRNA
This fragment contained the gene for GFP

15. Southern Blotting

16. Polymerase Chain Reaction
Technique used to make many copies of a gene
DNA polymerase enzyme first shown to be able to withstand heating and cooling cycles in bacteria from hotsprings of Yellowstone national park

17. How is the recombinant DNA used?
Is it possible to change the DNA of a living cell?
Griffith with his mice and bacteria experiments showed this was already possible

18. How can DNA fragments be combined?
DNA can be built in a lab, and inserted into cells
First step is to build the DNA sequence in a lab with the genes you want to include in the cell
DNA synthesizers produce short pieces of DNA up to several hudred bases in length
Sequences can be joined using enzymes such as DNA ligase that splices DNA together
Recombinant DNA is the joining of DNA from two or more sources, makes it possible to change the genetic composition of an organism

19. Plasmids and genetic markers
Initially there were problems with cells copying or replicating the new DNA
Nowadays Recombinant DNA is added to another piece of DNA that contains a ‘start’ signal – ensuring it is copied
Bacteria often contain plasmids – small circular DNA molecules
DNA is joined to a plasmid which then transforms the bacteria
Genetic marker allows transformed bacteria to be visible
Transformed bacteria can also have antibiotic resistance added so you are just left with a population of modified bacteria
Why is this process so useful?

20. Transgenic organisms
These involved incorporating genes from different species
Recombinant DNA is inserted into the genome of the host organism
Transgenic technology was perfected on mice
Possible to transform plants and animals
Increased our understanding of gene regulation and expression
Transgenic plants
Plants transformed using agrobacterium
In nature this bacterium contains plasmids that cause tumors
This tumor causing plasmid can be replaced with recombinant DNA
Transgenic animals
Animals can be transformed with some of the same techniques as plants
DNA can be injected into the nucleus of egg cells
Enzyme already there can help insert DNA into foreign cell
Nowadays gene replacement also possible – sequences of a chromosome can be replaced

21. Cloning
A clone is a member of a population of genetically identical cells produced from a single cell
A new individual is grown from a single cell from an adult organism
Cloning bacteria is easy, but multi- celled organisms are harder
Cloned tadpoles first produced in 1952
Dolly the sheep was cloned in 1997