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Topic 5 – Cloning ( by Ahmed, Zakaria Abshir, Talha )
Syllabus 4.4.11 Define clone
A group of genetically identical organisms or a group of cells derived from a single parent cell
Syllabus 4.4.12 Outline a technique for cloning using differentiated animal cells
Somatic Cell Nuclear Transfer (SCNT)
 A female animal, eg. a sheep, is treated with hormones, like FSH, to stimulate the development of eggs.
 The genetic information is removed from the egg cell by extracting the nucleus
 The cell is fused with the nucleus from a somatic cell of another sheep, making the egg cell diploid
 An electric shock is delivered to stimulate the egg to divide, and once this process has begun the egg is
implanted into the uterus of another ewe.
 The developing embryo will have the same genetic material as the sheep that contributed the diploid
nucleus, and thus be a clone
Syllabus 4.4.13 Discuss the ethical issues of therapeutic cloning in humans
Arguments for Therapeutic Cloning
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Can be used to cure serious diseases or disabilities with cell therapy ( replacement )
Stem cell research may encourage further future discoveries and useful technologies
Stem cells can be taken from embryos that died or stopped developing. For example, from aborted
babies.
Cells are taken at a stage when the embryo has no nervous system and can arguably feel no pain
Arguments against Therapeutic Cloning
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Humans have the power over the life of embryos
Embryonic stem cells are capable of continued division and may develop into tumors and cause cancer
Many embryos are destroyed because more are produced than needed
With additional cost and effort, alternative technologies may fulfil similar roles (e.g. nuclear
reprogramming of differentiated cell lines)
Basic nuclear transfer technique ( Dolly the sheep )
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An udder cell from a six-year-old Finn Dorset white sheep was kept in a growth medium to keep alive
during reprogramming.
The cell was injected into an unfertilised egg cell with no nucleus (The unfertilised egg cell came from a
Scottish Blackface ewe )
The cells were induced to fuse by using electrical pulses.
The cells were cultured for six or seven days to see if they divided and developed normally into embryo.
The embryo is implanted it into the uterus of another Scottish Blackface ewe. Dolly was born with a
white face.
From 277 cell fusions, 29 early embryos developed and were implanted into 13 surrogate mothers. But
only one pregnancy went to full term, and the 6.6 kg Finn Dorset lamb (alias Dolly) was born after 148
days.
Reproductive VS therapeutic cloning + Ethics
Reproductive cloning
 Occurs when a copy of another human being is created through SCNT, allowed to grow up to 14 days in
a petri dish, and then transplanted into a uterus to grow until birth.
 Reproductive cloning has been used to create Dolly the Sheep and many cloned cows, dogs, cats and
horses.
 There have been no successful attempts to reproductively clone a human being yet.
Therapeutic cloning
 Occurs when cloned embryos created through SCNT are allowed to grow for a few days and then killed
for their stem cells.
 It could help advance embryonic stem cell research.
 Human life begins at conception. Even if the young life is only five days old, it is still a human being
worthy of respect.
Resurrecting the Extinct Wholly Mammoth through Cloning
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Scientists are inserting mammoth DNA into elephant egg cells in an attempt to resurrect the now extinct
mammal
Through the use of CRISPR, a tool that aids in editing DNA scientists were able to splice the genes that
code for hair length and colour, ear size, subcutaneous fat from a mammoth’s genome and through
transgenesis insert these genes into the DNA of an elephant’s skin cell
Signifies the first time mammoth genes have been functional since they have gone extinct
Next step is to turn these elephant skin cells with woolly mammoth DNA into hybrid embryos by
enucleating them and placing them into enucleated elephant egg cells which will then be cloned to
produce hundreds of hybrid embryos
These hybrid embryos will go through gestation in artificial wombs once they are made as growing them
in an elephant host for example would cause all sorts of run ins with animal activists
Embryonic VS Adult Stem Cell usage
In regards to potential for cell-based regenerative therapy, there are differences in which the respective
Embryonic and Stem cells bring to the table.
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The first difference lies in the inherent ability of these embryonic cells or stem cells becoming a specific
type of differentiated cell.
Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem
cells are thought to be limited to differentiating into different cell types of their tissue of origin.
Large numbers of cells required in regenerative therapy. Embryonic stem cells are easily grown within a
culture. Adult stem cells are rare in mature tissues, and if found, isolating the cells from the tissue is an
issue. Also, adult stem cells cannot be grown in culture, there has yet to be found a methodology to
grow Adult stem cells.
It is believed that tissues derived from embryonic and adult stem cells can differ in the likelihood of
being rejected after transplantation. However it is not certain, since relatively few clinical trials have
tested the safety of transplanted cells derived from human embryonic stem cells.
Adult stem cells and tissues from the Adult stem cells are understood to be less likely to cause rejection
after transplantation. This is due to a recipients own cells being expanded in culture, coaxed into
assuming a specific differentiated cell type, and reintroducing the cells back into the patient. This is an
advantage over embryonic cells as they can be used for regeneration without the risk of rejection by the
immune system. Thus, with the help of immunosuppressives, the risk of rejection can be eliminated
entirely.
Current Regulations in Canada
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Cloning humans is banned
Cloning stem cells is banned
Growing human embryos is banned and so is the buying and selling of human embryos
Quiz
Multiple choice ( 4 marks )
1) What is a Clone?
A) A twin
B) A replica
C) Phenotypically similar but with distinguishable genotype
D) Cells derived from the same parent cell
2) Cloning can be done using SCNT. What does the acronym stand for?
A) Striated Cell Nuclear Therapeuting
B) Somatic Cell Nuclear Transfer
C) Secretin Cell Nuclear Transfer
D) Somatic Cell Nuclear Therapeuting
Short Answer ( 11 marks )
1) Outline the steps used for the cloning of differentiated animal cells in SCNT.
2) State three pros and three cons of therapeutic cloning.
TOTAL
( 5 marks )
( 6 marks )
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