Download 3.5 Genetic modification and biotechnology

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 DNA
Just 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)
PCR
Answer these questions
1) 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 strands
75 = optimum temperature for DNA polyermase
enzyme
Gel electrophoresis
Separate proteins according to size
In 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 Activity
Go to:
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 gel
3. 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 PCR
3. Copied DNA split into fragments using
enzymes
4. Fragments separated using gel
electrophoresis
5. Produces a pattern of bands that is always
the same with DNA from an individual
6. 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 modification
Transfer 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
Salmon
Salmon that grows twice as fast as normal
Vaccine bananas
Contain vaccines for diseases
Low methane cows
25% less methane – less impact on the environment
Gene transfer
Involves the use of plasmids, DNA ligase and
restriction endonucleases
Multiply bacteria containing gene
Separate and purify human insulin
Human insulin can then be used by diabetic
patients
What is a clone?
A clone is genetically identical to its “parent” (single
original parent)
Two types of reproduction
SEXUAL
Genetically
different
offspring
ASEXUAL
Genetically
identical
offspring
Sexual Reproduction
HUMANS
GAMETES
Sperm 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 cell
Offspring inherits features from both
parents
Variation 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 embryos
Break 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
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 sheep
As it is the nucleus from a body cell of the Finn
Dorset ewe Dolly is a clone of her.