DNA technology Ch. 10 Cloning genes
Into bacteriaInto plantsInto animals
Recombinant bacteriaCh 10 p. 281
Human Growth Hormone (hGH) cloned into bacteria (1980s)
Pituitary dwarfism mutation in hGH gene
hGH protein is produced by pituitary gland
Pre-1985 hGH from cadaver brains Drawbacks?
TodayhGH cloned
26 inches tall
Cloning steps:1. isolate hGH mRNA
from normal human
2. reverse transcribe to cDNA
How is cDNA different from DNA?
3. ligate hGH cDNA into plasmid vector
4. transform bacteria grow bacteria and they express hGH
5. purify protein
Other cloned drugs made by bacteria Human insulin for diabetics 1987Factor VIII for hemophiliacs 1993Interferon for chemotherapy 1993EPO for anemia 1992FSH for fertility clinics 1996TPA to prevent blood clots 1996Hepatitis B vaccine
bGH to increase milk yield in cows
Advantages of rbacteria/drugsCleanWorlds supply in one labCheap ?
When rBST injected into cows digestive systems are more efficient at converting feed to milk. 8 gallons of milk/day/cow 9
120 studies have found no differences in milk from rBST-supplemented cows. National Institutes of Health, the Congressional Office of Technology Assessment and the drug-regulatory agencies of Britain, Canada and the European Union, Department of Health and Human Services
Traces of BST are found in milk from all cows, supplemented or not. rBST is broken down in the human gut, does not enter blood stream
Even if injected into the human bloodstream, has no biological activity.
What do you think?
Affect of high human growth hormone in childhood
….. Pituitary tumor
Cloning into plants (GM) pg 282Transgenic plants
Plants acquire new genetic trait by direct introduction of gene
We have been modifying plant genes by breeding for 1000’s of years
Getting a gene into a plant embryo
A natural system:
Agrobacterium tumefaciens bacteria infects plants crown gall disease (tumor) at wound sites
Agrobacterium tumefaciens cells attached to a plant cell. From Genome News Network and Martha Hawes.
1. Engineer Ti plasmid Remove tumor inducing genes Add gene of interest
2. transform agrobacterium with Ti plasmid
Ti plasmid is 200kb
3. wound plant and infect with agrobacterium
4. gene of interest transferred to plant cell
Infection stimulates excision of 30 kb region of Ti called T-DNA insertion into chromosome
ssT-DNA~20kb excised
5. grow explant
= transgenic plant
Agrobacterium tr ns n pl nta ge ic a Virigina Tech
Why is this referred to as horizontal gene transfer?
How could this be used to introduce engineered genes into a plant cell?
Last year, 12 million farmers in 23 countries grew 282.4 million acres (114.3 million hectares) of GM crops
genetically modified foods in US do not require labeling to notify consumers.
GM plants 2007
genetically modified plants
iron-storage gene from wild soybeans and vitamin E has been enhanced by the use of genes from rice and rock cress. 2008
Resistance gene to potato beetle have been approved in the US and in Canada.
Fungus chitinase gene
Nicotine-free GM tobacco
Osmotin gene to tolerate salt stress
Benefits Increased crop yieldResistance to drought, freezing Decreased use of pesticideDecreased use of herbicides Increased nutrition Increased shelf lifeCan remove allergens
Drawbacks increased seed costspesticide resistant bugsnew allergensharmful to insects?may spread to other plants
Bacillus thuringiensis (Bt) produce a protein crystal toxic to insects.
The toxin genes are on a plasmidThe proteins bind to receptors in insect's
intestine. Humans do not have these receptors…………………….
Bt transgenic corn Ch. 10 pg. 284Corn engineered with gene
that codes for a Bt toxin
More on Bt corn Univ. MN
Non engineered cotton Bt cotton
Effect of insect infestation on cotton
http://cls.casa.colostate.edu/TransgenicCrops/what.html
Mustard plant genetically engineered to remove selenium from soil
Can then grind and use in selenium deficient soils
Golden Rice Oryza sativa 2012!
Vitamin A deficiencyLeading cause of childhood blindness (500,000 new
cases /year)
Engineer rice to produce genes needed for carotene in endosperm (phytoene synthase and phytoene desaturase)
Tissue specific expression cassette
One serving of golden rice supplies enough beta-carotene to meet 10 percent of the daily requirement for Vitamin A
Promoter--- transit sequence--- gene--- -
Do we need legislation for labeling of GM foods?
Should GM genes, plants, animals, be patented?