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.