3.5 Genetic modification and biotechnology Understanding: -Gel electrophoresis is used to separate...
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Transcript of 3.5 Genetic modification and biotechnology Understanding: -Gel electrophoresis is used to separate...
3.5 Genetic modification and biotechnology
Understanding:- Gel electrophoresis is used to separate
proteins of fragments of DNA according to size
- PCR can be used to amplify small amounts of DNA
- DNA profiling involves comparison of DNA - Genetic modification is carried out by gene
transfer between species- Clones are groups of genetically identical
organisms, derived from a single original parent cell
- Many plant species and some animal species have natural methods of cloning
- Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells
- Methods have been developed for cloning adult animals using differentiated cells
Applications:- Use of DNA profiling in paternity and forensic
investigations- Gene transfer to bacteria with plasmids using
restriction endonucleases and DNA ligase- Assessment of the potential risks and benefits
associated with genetic modification of crops- Production of cloned embryos by someatic cell
nuclear transfer
Skills:- Design of an experiment to assess one factor
affecting the rooting of stem cuttings - Analysis of examples of DNA profiles - Analysis of data on risks to monarch
butterflies of Bt crops
Nature of science:- Assessing risks associated with
scientific research: scientists attempt to assess the risks associated with genetically modified crops or livestock
Polymerase Chain Reaction
Amplify small amounts of DNAJust need a single molecule of DNA to make
millions of copies
Able to study DNA without using up the whole sample
- DNA from fossils- DNA from crime scene (hair, semen or blood)
PCRAnswer these questions1) What are the ingredients for PCR?2) What are primers?3) Why must the mixture be heated/cooled to about
95°C? 55-60°C? 72°C?
Answers
1. Template DNA, DNA primers, Deoxynucleotide triphosphates, thermophilic polymerase with a
buffer
2. Primers start the chain reaction
3. 95 = DNA strands separate as hydrogen bonds break
55-60 = Primers bind to single DNA strands75 = optimum temperature for DNA polyermase
enzyme
Gel electrophoresis
Separate proteins according to sizeIn an electric field
Samples placed into wells in a gel
Electrical field applied
Charged molecules move through the gel
Small fragments move faster than large ones
Gel Electrophoresis ActivityGo to: http://learn.genetics.utah.edu/content/labs/gel/
Answer the following questions:1. What is the gel made up of?2. What is the purpose of the buffering solution that the
gel is immersed in?3. Why are known DNA fragment lengths/size standards
needed?4. How does the gel separate DNA strands of different
lengths?
Answers
1. Powdered agarose, buffer (Jell-o)2. Salt water solution that allows electrical
charges to move through the gel3. Compare your bands to bands of known length to help you identify the length of DNA
4. DNA moves through gel repelled by negative charge – smaller moves further away
DNA profiling
1. Sample of DNA obtained 2. Sequences selected and copied by PCR3. Copied DNA split into fragments using
enzymes4. Fragments separated using gel
electrophoresis5. Produces a pattern of bands that is always
the same with DNA from an individual6. Compare profiles of individuals to see which
bands are similar or different
Compare DNA at a crime scene with suspects DNA
Paternity tests
- Men claim they are not the father
- Mother has multiple partners and isn’t sure
- Child wishes to prove they are an heir
Genetic modificationTransfer of genes between
species
Genetic code is universal = amino acid sequences
translated from genetic code is unchanged
Same polypeptide is produced
Genetic modification- Gene for making human insulin to bacteria- Goats produce milk that contains spider silk- Many GM crops
SalmonSalmon that grows twice as fast as normal
Vaccine bananasContain vaccines for diseases
Low methane cows25% less methane – less impact on the environment
Gene transfer
Involves the use of plasmids, DNA ligase and restriction endonucleases
Restriction endonuclease enzyme cuts
DNA
DNA ligase fixes the strands
together
Multiply bacteria containing gene
Separate and purify human insulin
Human insulin can then be used by diabetic patients
Enzyme also cuts bacterial DNA
This produces a lot of insulin for human use
Separate and purify insulin
Insert insulin gene using DNA ligase
Cut out insulin using restriction endonuclease
Bacteria now contains insulin gene
Locate the cell that contains insulin
Multiply bacteria in a fermenter
3. Enzyme also cuts bacterial DNA
7. This produces a lot of insulin for human use
8. Separate and purify insulin
4. Insert insulin gene using DNA ligase
2. Cut out insulin using restriction endonuclease
5. Bacteria now contains insulin gene
1. Locate the cell that contains insulin
6. Multiply bacteria in a fermenter
What is itHow is it done
What is it useful for (Use examples) Advantages and disadvantages
(summarise page 192-194 all boxes!)
Benefits Risks
Environmental Fewer chemicals used and leaked into the
environmentLess eutrophication
Out crossing of genesAlter ecosystemsAffect food chains
If some plants are pesticide resistant – a lot of pesticides can be used then just to be
sure pests are deadHarm to other organisms
Health Increase mineral/vitamin content
Decrease starvation (Sustainable way to feed
the world)
Allergic reactions (do not know where a gene comes
from)Fewer nutrients
Ethical issues
Agricultural Reduce pesticides (spend less money)
Increased yieldsMore aesthetically
pleasing
Affect other organisms other than the target pests
Bt corn
Produces a toxin to protect them from corn pestsWind pollinated plant
Pollen which also contains toxin blown awayMonarch butterflies die
For or against
Many studies carried outStudies need to be carried out over large periods of
time to see if there is a significant issueMany studies accused of being biased for/against
GMOs
GM good = GM companiesGM bad = organic farmers
What is a clone?
A clone is genetically identical to its “parent” (single original parent)
Two types of reproduction
SEXUAL Genetically different offspring
ASEXUALGenetically identical offspring
Sexual ReproductionHUMANSGAMETESSperm cell: Egg cell:
Each gamete contains 23 single chromosomes Half the number of that in a normal cell (23 pairs)
These are haploid cells
Sexual Reproduction
FERTILISATION
Gametes fuse together
Form a cell with 23 pairs of chromosomes
This is a Diploid cellOffspring inherits features from both parentsVariation in offspring
Advantages
SEXUAL REPRODUCTION
Variation in offspring means they are able to - Adapt to surroundings- Evolve
Asexual Reproduction
An ordinary cell can make a new cell by dividing in two
New cell has exactly the same information as parent cell
No fertilisation between male and female gametes
Some plants and bacteria produce offspring asexually (some animals do too when no males around)
Advantages
ASEXUAL REPRODUCTION
• Very quick • Bacteria can produce offspring in 20 mins • If already adapted to habitat – good to be identical
Cloning animal embryosBreak up embryo into more than one group of cells
All cells in an early animal embryo are able to develop into any type of tissue
Cloning animal embryos
Sometimes this happens naturally
Can also be done artificially
Cannot tell whether the individual has
the desired characteristics
Cloning Adults
Harder than cloning embryos
as cells have already
differentiated into different tissue
cells
Dolly the sheep
Somatic-cell nuclear transfer
1. Adult cells taken from udder of Finn Dorset ewe and grown in the lab (udder contains some stem cells)
Dolly the sheep
2. Cells grown in a medium of nutrients
Genes in the cells become inactive
Pattern of differentiation was lost
Dolly the sheep
3. Unfertilised eggs taken from ovaries of a Scottish Blackface ewe
Nuclei were removed from these eggs
Dolly the sheep
4. Electric pulse used to fuse the two cells together
10% of the fused cells develop into an embryo
Dolly the sheep
5. Emrbyos injected when around 7 days old into the uteri of surrogate mother ewes
One out of 29 was successful = DOLLY!
Who does Dolly look like?
Dolly the sheepAs it is the nucleus from a body cell of the Finn
Dorset ewe Dolly is a clone of her.