Transcript Biotechnology

Biotechnology
4.4 Syllabus points
4.4.1 PCR

Outline use of PCR to copy and amplify minute
quantities of DNA
PCR = polymerase chain reaction
Helps to get enough DNA to analyze when a sample is
very small
Thermocycler - machine automates the copying of the
DNA
Millions of copies in a few hours
PCR
Uses DNA polymerase from bacteria that lives in hot
springs Thermus aquaticus
3 steps
Denature – heat up breaks double into single strand
(about 98 degrees C)
Anneal – cool and primers can attach to either a top or
bottom strand
Extension – Taq polymerase makes complementary
strand
PCR
Repeated cycles of heating and cooling stimulates the
primers to attach to copies and copies of copies
Result is exponential increase in number of copies of
DNA
4.4.2

Gel electrophoresis separates DNA by size as move
in electric field
DNA negative charge move towards positive pole
Agarose gel forms mesh of cross linked polymers
DNA stained to visualize the separated bands
4.4.3

Gel electrophoresis of DNA used in DNA profiling
Matching an unknown sample with a known to see if
they match up is DNA profiling
Identical band patterns means that is the individual in
question – similar patterns usually mean the
individuals are relatives
4.4.4 Applications of
DNA profiling

Paternity – legal identification of biological father

Forensic investigations – compare samples from
crime scene with suspect

Cold cases reopen with new DNA technology such
as PCR

Release of wrongly imprisoned individuals
4.4.5 Analyze gels

Use gel banding patterns to determine matches
between individuals to solve crimes or determine
paternity
4.4.6 Human Genome
Project

Outline three outcomes of sequencing the complete
human genome
1990-2003 international effort
Government and private labs
Aimed to identify the entire sequence of bases in
human DNA
Created in essence a map of all genes on all 23
chromosomes
4.4.6 Human genome

Allows identification of location of genes causing
diseases

Production of new medications by identifying
products made by healthy individuals determine the
gene responsible copy the gene and use it to produce
the desired molecule

Evolutionary relationships and migration patterns of
humans
4.4.7 Gene transfer

Genes can be transferred between species because
DNA is universal language and code for the same
amino acids

So gene will produce the same protein no matter
what organism it is placed into
Examples gene transfer

Cold resistant tomatoes

Bt-corn (Bacillus thuringiensis)

Spider silk goats
4.4.8 Technique Gene
Transfer

Cut and paste genes using restriction enzymes AKA
endonucleases find and cut at target sequences

Paste genes using DNA ligase enzyme which
recognizes the sticky ends of the fragments and
attaches them
Copy paste using plasmid
DNA

Use host cell often Escherichia coli or yeast

Prokaryotes most DNA in single chromosome but
also have extra DNA is small loops called plasmids

To copy DNA it needs to be pasted into a plasmid
4.4.8 Pasting into plasmid

Remove plasmid from cytoplasm of bacteria

Cut open plasmid using restriction enzyme

Paste new gene using DNA ligase into the open
plasmid

Modified plasmid called a recombinant plasmid

Recombinant plasmid used to deliver new gene into
genome of target organism
4.4.9 Genetically Modified
organisms

Golden rice – beta carotene into rice prevent
blindness

Salt resistant tomatoes
Proponents – will help solve world hunger
Critics – world hunger is distribution not production
issue
4.4.10 Benefits/Risks
GMO
Benefits:
•
Improve food production
•
Reduce chemicals if plants have own pest control
substances
•
Reduce cost and pollution of making medicines
•
Farmers have added control of crops and livestock
•
Globally GM crops need less water and pesticides
4.4.10 Risks
Risks- long term risks unknown
•
Pollen escapes into wild integrated possibly into wild genome
•
Genes could cross species – seen in labs could it happen in
wild?
•
Bt crops harmful to humans – pesticide throughout plant not
just on surface
•
Allergies
•
Large corporations will own large part of food supply
•
High tech not always better than simple solutions
•
Decrease in biodiversity
4.4.11 Cloning

Define clone
Group of identically identical organisms or group of
cells artificially derived from a single parent
Farmers have cloned plants for years by regenerating
plant material
4.4.12 Technique cloning

Enucleate unfertilized egg and transfer nuclear
material from donor cell

Electrical current fuses egg and nucleus

Zygote divides and forms embryo which is implanted
in surrogate mother

Donor cell may be adult differentiated cell (non
gamete) rather than from an egg cell

Offspring is clone of donor organism
4.4.13 Ethics therapeutic
cloning

Cloning using undifferentiated cells

AKA embryonic stem cells

Requires production of human embryos

Is it ethical to generate new humans for medical
research?

However, stem cells allow repair of burns, new heart
muscle, new kidney tissue
Types of Cloning

Therapeutic cloning makes new tissues

Reproductive cloning makes new organisms