Slides covering material from Topic 3.5 of the updated IB Biology syllabus for 2016 exams

1. Genetic Modification
& Biotechnology (3.5)
IB Diploma Biology
Essential Idea: Modern
understandings of genetics and
biochemistry allow biologists
to modify and manipulate the
traits of organisms

2. 3.5.1 Gel electrophoresis is used to separate proteins or fragments of DNA
according to size and charge.
Gel Electrophoresis:
• Samples of either DNA or protein
are inserted into wells in a gel
• Gel is placed in a conducting fluid
and a current is passed through it
• Molecules move through gel based
on their charge (ex. DNA molecules
move to positive electrode since
they’re negatively-charged)
• Smaller fragments / molecules move
further through the pores in the gel,
while larger pieces don’t travel as far

3. 3.5.2 PCR can be used to amplify small amounts of DNA.
The Polymerase Chain Reaction (PCR)
Synthetic method of amplifying specific
sequences of DNA. Useful when only a small
amount of DNA is available for testing e.g. crime
scene samples of blood, semen, hair, etc.
http://highered.mcgraw-
hill.com/olc/dl/120078/micro15.swf
• Processes artificially recreates DNA replication
• Taq DNA Polymerase is used for PCR
• Comes from heat-resistant bacterium, Thermus
aquaticus, that lives in hot springs…
• Can resist denaturation at high temperatures
required to separate DNA strands in PCR
• Copies up to 1000 nucleotides / minute

4. 3.5.2 PCR can be used to amplify small amounts of DNA.
The PCR Process:
PCR occurs in a thermal cycler and involves 3 steps:
1. Denaturation: DNA sample is heated to
95⁰C to break hydrogen bonds and separate it
into two strands
2. Annealing: DNA sample is cooled to 54 ⁰C,
allowing primers attach to opposite ends of the
target sequence
3. Elongation: A heat-tolerant DNA
polymerase (Taq) copies the strands
• One cycle of PCR yields two identical copies of
the DNA sequence
• A standard reaction of 30 cycles would yield
1,073,741,826 copies of DNA (230)

5. 3.5.3 DNA profiling involves comparison of DNA.
http://learn.genetics.utah.edu/content/labs/gel/
http://www.dnalc.org/resources/animations/gelelectro
phoresis.html

6. 3.5.3 DNA profiling involves comparison of DNA.

7. AHL: 7.1.8 Explain how tandem repeats are used in DNA profiling.
• Variable Number Tandem Repeats
(VNTRs) are short base sequences that
show variation between individuals in
terms of the number of repeats
• These are examples of Highly
Repetitive Sequences – useful for DNA
profiling due to uniqueness

8. 3.5.9 Use of DNA profiling in paternity and forensic investigations.
Forensic Investigations:
• Straightforward – just look
for a full match between
the DNA sample and the
potential suspects
Paternity Investigations:
• More complicated – since offspring inherits a mix of DNA from parents,
the child will show bands unique to each parent
• Each band in the child’s profile must match to a either a band in the
mother’s profile OR a band in the father’s profile (usually ~50-50 split)

9. 3.5.14 Analysis of examples of DNA profiles.

10. 3.5.14 Analysis of examples of DNA profiles.

11. 3.5.14 Analysis of examples of DNA profiles.

12. 3.5.14 Analysis of examples of DNA profiles.

13. 3.5.14 Analysis of examples of DNA profiles.

14. 3.5.14 Analysis of examples of DNA profiles.

15. 3.5.14 Analysis of examples of DNA profiles.

16. 3.5.14 Analysis of examples of DNA profiles.

17. 3.5.14 Analysis of examples of DNA profiles.

18. 3.5.14 Analysis of examples of DNA profiles.

19. Since the genetic code is universal,
genes can be transferred between
species and still allow for the same
polypeptide to be translated.
Gene transfer can be used to give
organisms new characteristics usually
only found in other species.
Left, a tobacco plant that has been
modified by the addition of a glowing
gene (for the enzyme Luciferase)
naturally found in fireflies.
These organisms are known as GMOs
or Transgenic organisms
3.5.4 Genetic modification is carried out by gene transfer between species.

20. 3.5.4 Genetic modification is carried out by gene transfer between species.

21. 3.5.4 Genetic modification is carried out by gene transfer between species.

22. 3.5.10 Gene transfer to bacteria with plasmids using restriction
endonucleases (enzymes) and DNA ligase
Transferring genes into bacteria, such as E. coli
requires plasmids, restriction endonucleases, and
DNA ligase enzymes
• An mRNA transcript encoding the desired
protein is obtained from the eukaryotic cell and
then made into cDNA (complimentary DNA
using reverse transcriptase)
• Not only is mRNA easier to extract (since
eukaryotic DNA is bound up with histones in the
nucleus), but this also ensures the inserted gene
will already be spliced and have no introns
(which bacteria do not have)
• A bacterial plasmid and the eukaryotic cDNA are
both cut with the same restriction enzymes
• DNA Ligase is used to seal the eukaryotic
sequence into the bacterial plasmid

23. 3.5.11 Assessment of the potential risks and benefits associated with genetic
modification of crops.
GMO Description
Golden Rice
Rice modified with daffodil genes to have more
beta-carotene, which body converts to Vitamin A
Salt-
resistant
Tomatoes
Tomatoes modified to grow well in saline soils
Bt Corn
Corn modified with a bacterial insecticide gene so
that it produces insect toxins within its cells
Factor IX
Sheep
Sheep modified with human clotting factor IX gene
so that they produce clotting factor in their milk for
hemophiliacs
Round Up
Ready Soy
Soybeans modified with a herbicide resistance
gene so farmers can spray fields and kill weeds, not
soybean plants
Rainbow
Papaya
Papaya modified with viral genes that make it
immune to the Papaya Ringspot Virus

24. 3.5.11 Assessment of the potential risks and benefits associated with genetic
modification of crops.
Benefits of GMOs
Environmental Health Agricultural
Pest-resistant crops mean
less chemical insecticides
are used
Less need to plow and
spray crops also save fuel,
reduced carbon footprint
Improved shelf-life
means less wasted /
spoiled food in stores
Nutritional value of foods can
be improved by enhancing
vitamins
Crops can be produced that
lack natural allergens or toxins
GM crops can be engineered
to produce cheap, edible
vaccines
GM bacteria produce cheap
medical compounds such as
insulin and clotting factor
Crops can be made to be
drought, cold, and salinity-
resistant, expanding range for
farming and increasing crop
yields
Herbicide resistant GM crops
allow for easy killing of weeds
that sap nutrients from crop
plants
Crop varieties can be produced
that are resistant to viruses

25. 3.5.11 Assessment of the potential risks and benefits associated with genetic
modification of crops.
Risks of GMOs
Environmental Health Agricultural
Toxins in pest-resistant
GMOs could negatively
impact non-target
organisms and harm
ecosystems
Cross-species pollination
could spread herbicide
resistance genes and create
‘super-weeds’
Biodiversity could be
negatively affected by
destruction of pests, weeds,
and even competing plants
Proteins transcribed and
translated from transferred
genes could cause allergic
reactions in humans or other
animals – currently GM foods
are not necessarily labeled
Antibiotic resistance genes
used as markers during gene
transfer could spread to
pathogenic bacteria
Transferred genes could
mutate and cause
unexpected risks
GMOs with pest toxins could
increase evolution of
resistance in certain pest
populations
Big biotech companies hold
monopolistic legal rights
(patents) over GM seeds and
farmers must pay large sums
for seeds each year. They are
not permitted to save and re-
sow seeds, so strains are not
able to adapt to local
conditions.

26. 3.5.15 Analysis of data on risks to monarch butterflies of Bt crops
Previously, farmers would protect crops
from pests by spraying with chemical
pesticides. Today, may crops are
genetically-modified with a gene from
the bacterium Bacillus thuringiensis (Bt)
that produces a protein toxic to insects
The Bt toxin kills targeted pest like the
corn-borer worm, but also kills non-
target insects
Monarch butterflies feed on milkweed
which often grow near Bt crops. When
pollen from the Bt crops ends up
dusting milkweed plants, butterflies
consume the toxin and die
In the graph above, blue
represents plants not
dusted with any pollen,
yellow represents non-
GM pollen dusting, and
red represents Bt pollen
dusted milkweed plants

27. 3.5.5 Clones are groups of genetically identical organisms, derived from a
single original parent cell
Clone:
A group of genetically-identical organisms
derived from a single original parent cell
Organisms that reproduce asexually always
produce genetically-identical offspring (clones)
Clones are rarer in sexually-reproducing
organisms (i.e. monozygotic twins)
A clone can be very large, such as in the case of
commercially grown potatoes, but it can always
be traced back to an original parent cell.

28. 3.5.6 Many plant species and some animal species have natural methods of
cloning
Many plants can naturally produce
clones (term derives from Greek
word for twig)
Examples:
• A single garlic bulb will clone itself to
form many identical bulbs in a
growing season
• Strawberry plants grow stems with
plantlets that can become
independent parent plants
• Hydra create clones by budding

29. 3.5.13 Design an experiment to assess one factor affecting the rooting of
stem cuttings
A stem cutting is a short length of plant stem that can be used to clone a plant. If
roots develop from the cut stem, it can become a new, independent parent plant
Nodes are parts of stem where leaves attach. Cuttings are made below nodes.
Normally takes several weeks for ‘rooting’ (new root growth)
Possible factors to study:
• Cutting above or below node
• Length of cutting
• Whether end is left in air or
compost / water
• How many leaves are left on
• Use of hormone root powder
• Type of compost
• Temperature

30. 3.5.7 Animals can be cloned at the embryo stage by breaking up the embryo
into more than one group of cells
In early stages of embryo
development when cell are still
pluripotent, an embryo can be
fragmented or split to create animal
clones. This is how monozygotic twins
can occur in humans.
Animal embryos created through in
vitro fertilization can be artificially
fragmented and then transplanted
into surrogate mothers. This is most
effectively done when the embryo is
at the 8-cell stage
Less interest in this cloning process since the 8-cell embryo
stage is still too early to assess if a clone will have desired
traits or not…

31. 3.5.8 Methods have been developed for cloning adult animals using
differentiated cells
In the 1950s, John Gurdon, then a
student at Oxford, removed the
nucleus from the body cell of a
tadpole and transplanted the nucleus
into a tadpole egg cell.
The egg cell with the transplanted
nucleus developed as a normal zygote
and created a tadpole with the same
genome as the body cell nucleus
In 1996, Dolly the sheep became the
first mammal cloned in this way
In 2012, Gurdon received the Nobel
Prize in Medicine for his research

32. 3.5.12 Production of cloned embryos by somatic cell nuclear transfer
https://www.hhmi.org/biointeractive/somatic-
cell-nuclear-transfer-animation
Cloned embryos, such as Dolly, are
produced by a process called Somatic
Cell Nuclear Transfer (SCNT)
1. Somatic cells are taken from adult organism to
be cloned and grown in a low-nutrient medium.
This inactivates genes to wipe out any previous
pattern of differentiation
2. Unfertilized egg cells are taken from a female of
same species and their nuclei are removed
3. Cultured somatic cells and enucleated egg cells
placed side-by-side and zapped with a small
electric pulse to fuse them together (about 10%
of cells fuse)
4. Fused egg cells containing somatic cell nucleus
develop into embryos for seven days and are
then implanted into surrogate mother (in the
case of Dolly, only 1 of 29 successfully implanted
and completely developed)

33. 3.5.12 Production of cloned embryos by somatic cell nuclear transfer

34. 3.5.12 Production of cloned embryos by somatic cell nuclear transfer

36. Bibliography / Acknowledgments
Bob Smullen