Download CLONING

CLONING
Goals: Be able to…
• Differentiate between different types of cloning.
• Different types of cloning
• Describe how somatic cell nuclear transfer
works.
• Reproductive cloning
• Define stem cells and differentiate between adult
and embryonic forms.
• Therapeutic cloning
• Stem cells
• List some applications of stem cell therapy.
• Describe the current status and issues
surrounding therapeutic cloning and stem cells.
http://stemcells.nih.gov/
http://www.ornl.gov/sci/techresources/Human_Genome/elsi/cloning.shtml
Different types of cloning
Embryo Cloning: Forming identical twin
embryos from a single embryo.
• Sea urchins (1872) and salamanders (1902).
• Embryo cloning
• Reproductive cloning
• Therapeutic cloning
Monozygotic twins (identical)
Reproductive Cloning: replicating an
organism using its complete genome.
Involves Somatic Cell Nuclear
Transfer (SCNT).
Normal fertilization
½ DNA
½ DNA
Complete
set of DNA
In vitro fertilization: Sperm + egg unite in lab
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SCNT
Surrogate
mother
Organism to
be cloned
1. Harvest the
nucleus of a
somatic cell
Egg develops
into embryo
1. Destroy the
egg cell nucleus
Embryo implanted into
surrogate mother to
develop cloned baby!
2. Implant harvested
nucleus into egg cell
Egg with cloned
nucleus
Fig 8.22
2. Are these mice genetically related to their
mother or their nuclear donor?
Potential to clone endangered species?
banteng
mouflon
Potential to clone extinct species?
• Dinosaurs
• Wooly Mammoths?
Problems with Reproductive Cloning
Cloned animals
Reproductive Cloning in Humans?
• Some genes not expressed normally.
• Problems in “reprogramming.”
3. What are some reasons why people might
want to reproductively clone humans?
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Therapeutic Cloning: Creating an embryo from a
DNA donor in vitro for medical purposes.
Reproductive cloning
4. What is the difference between the procedures
used for reproductive and therapeutic cloning?
SCNT
Therapeutic cloning
Use stem cells from embryo
Stem Cells: unspecialized, reproduce indefinitely,
and can differentiate into specialized cells.
5. Why would might people want to participate in
therapeutic cloning?
animation
Human cloned embryo only grew to 6 cell stage
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Blood vessel repair
Other Possible Therapies
Organ generation
Embryonic Stem Cells
• Insulin-producing cells.
• Repairing blindness.
• Neurons for Parkinson’s patients?
Different chemical
conditions
animation
Source: Excess embryos from in vitro fertilization
Embryonic stem cells:
Some adult stem cells
are flexible
All cell types
Adult stem cells:
Bone marrow cells
Some cell types
But… body makes 220
different types of tissues
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Why don’t we just use adult stem cells?
• Few tissue types.
• Difficult to isolate.
• Difficult to culture in large numbers.
• Chromosomally aged…?
4. What are the differences between adult and
embyronic stem cells?
More research on adult and umbilical cord stem
cells is needed…
Bush and US Funding policy:
Authorizes only lines already present in Aug, 2001.
19 lines of 60 are viable.
Recent advancements in stem cell science
• Embryonic stem cells from cells removed for
genetic testing
• Embryonic stem cells from “dead” embryos
• Adult stem cells cultured into neurons
Problems
• Grown on mouse
“feeder” cells… now
contaminated?
Recently…
• Accumulating
mutations over time
Michael J Fox
A cloned organism would be genetically most
similar to its
Which of the following best describes the
relationship between reproductive and
therapeutic cloning?
a. Surrogate mother.
b. Paternal gene donor.
c. Somatic nuclear donor.
d. Haploid nuclear donor.
A. They both use fertilized embryos.
B. Reproductive cloning uses gametes, while
therapeutic does not.
C. Reproductive cloning uses eggs, while
therapeutic does not.
D. Reproductive cloning involves implanting an
egg into a surrogate mother, while therapeutic
does not.
E. They are equally ethically contentious.
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The embryonic stem cells currently in use for US
govt.-funded research
A. Are taken from aborted fetuses.
B. Would probably become babies someday.
C. Are adequate for all future stem cell research.
D. Are no different than stem cells taken from
adult bone marrow.
E. None of the above.
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