Download Roslin Technique

introduction
This part is intended to provide the necessary background information for teacher to
lead the learning activities. Teacher is not expected to have an in depth understanding
of the scientific aspect of cloning as the focus of this case study is placed on the issue
area. But it is necessary for the teacher to have some fundamental concepts of life
science and the techniques of cloning. The later section of this part would give teacher
an overview of the ethical, legal and social issues of cloning. It should be remembered
that this part of information is not the teaching materials for students. Student learning
is done by the participation of the learning activities. Students are also expected to
perform the active role of learning via information searching, presentation and
discussion. Not only teacher can assess the performance of students, assessment by
classmates can be included which in turn can stimulate the interest and participation
of students.
Basic Life Science Terms
Cells
All living organisms contain cells, which are the fundamental working units of life. A
cell can be divided into two parts: the nucleus and the cytoplasm. Living cells take in
food and water. Cells can be organized to form tissues and organs.
DNA
The full name of DNA is deoxyribonucleic acid, which is the basic hereditary unit of
life. DNA coiled up to form a structure called chromosome. DNA can be found in the
nucleus of the cell. DNA controls the cellular activities. The DNA molecule is
arranged as a double helix, which is composed of nucleotides. Each nucleotide
consists of a sugar, a phosphate and a nitrogenous base. There are four different bases
in DNA. The DNA sequence is the particular side-by-side arrangement of bases along
the DNA molecule. The order of bases is important in determining the characteristics
of an organism.
Genome
It is the complete set of genetic materials in an organism.
Gene
It can be regarded as the specific segment of DNA in chromosomes that encodes
instructions on how to make proteins, particularly enzymes which catalyses the
biochemical reactions inside the body.
Proteins
Protein is a polypeptide, a kind of polymer, made up of the basic units of amino acids.
Proteins are the major components of cellular structures and enzymes. Enzymes
control the metabolic activities in cells.
Nucleus
containing
Nucleus
containing
DNA
DNA
Many other
cellular
structures
in
cytoplasm
Fig.1 The structure of a cell
Proteins control
cellular activities
Proteins
Genes
Chromosomes
Cell
DNA
Genes direct protein synthesis
Fig.2 DNA and protein
Websites
Please refer to ‘Background Information for Teachers  References’.
Cloning Techniques
What is cloning?
Clone is derived from the Greek klon, meaning, “twig”. It implies that if one
broke a twig from trees and then planted again, a copy of tree were obtained.
Nowadays, cloning is recognized as the process of making genetically identical
organisms through nonsexual manner. It has been widely practiced to produce plants
for many years. The first mammal cloning is a sheep named Dolly born in 1997.
The main reason for cloning is to produce organisms with desired qualities in large
quantity. There may be other reasons for cloning like the conservation of endangered
species or the replacement of lost or deceased pets.
What are the differences between clones?
Clones can be regarded as a set of genetically identical organisms. However,
clones are never identical even they may contain identical chromosomes. It is because
environmental factors can influence the expression of characteristics and development
of behavioural traits in mammals. Moreover, mutations do occur in individual
organism causing differences between clones.
What are the ways to clone mammals/humans?
Basically, there are three ways to cloning.



Twinning
The Roslin technique
The Honolulu technique
Twinning
Twinning can be viewed as splitting off a cell from an embryo. Once sperm
has fertilized an egg to form a zygote which would begin dividing. When the cells
divide into an eight-cell embryo and these eight cells are separated, they can be
implanted into the uteri of eight separate mothers. Thus eight clones will be obtained
from different mothers.
Twining
1. A sperm cell
combines with
an egg cell to
from aazygote.
zygote.
form
Sperm cell
Egg cell
Zygote.
2. The zygote
divides into
Dividing zygote
two cell.
Cell divided from division
3. The zygote
divides into
two cell.
4. The two cell develop into identical embryos,
which grow into natural identical twins,
who are clones of each other.
Fig.3 Twinning
The Roslin Technique
The Roslin Technique named after the Roslin Institute, where Ian Wilmut
developed for the creation of first clone (Dolly) from adult cells. This technique is
also known as nuclear transfer. In nuclear transfer the nucleus, which is part of a cell
and contains the DNA molecules from an unfertilized female egg cell, is carefully
removed to eliminate the majority of its genetic information. Unfertilized cells are
more likely to accept the donor nucleus as its own. The donor cell is then forced into a
dormant phase, which causes the cell to shut down but not die. In this state, the
nucleus is ready to be accepted by the egg cell. The donor nucleus is then placed
inside the unfertilized egg cell by transplantation.
An electric pulse is applied to the donor cell and the unfertilized egg cell,
which causes them to fuse together like soap bubbles. A second pulse causes the cell
to divide. Then the cell is manipulated as if it has been fertilized and is then implanted
into the uterus of the mother. The embryo develops into a foetus and is born
afterwards.
The cloned baby shares the exact DNA with the donor, just like an identical
twin. Only the clone is much younger than the twin of the donor. This technique
allows the production of genetically identical groups of animals, which possess a
desirable genetic trait. The followings show the essential steps involved in cloning an
animal.
Unfertilised egg cell
Donor cell
Nucleus
Step 1: Remove the nucleus of an egg cell.
Fig.4(a) Roslin Technique
Egg cell without nucleus
Adult donor cell (suspended state)
Step 2: Starve the donor cell by not supplying nutrients so as to
match withthe state of the egg cell.
Fig.4(b) Roslin Technique
Egg cell without nucleus
Adult donor cell (suspended)
Step 3: Use electric current to fuse the donor and egg cells. The donor
cell’ nucleus can direct the development of the egg cell.
Fig.4(c) Roslin Technique
Sheep
Developing Embryo
Oviduct
Step 4: Place the developing egg cell in the oviduct of a sheep for six days.
The oviduct provides a place for the egg cell to grow into embryo.
Fig.4(d) Roslin Technique
Surrogate Mother
Step 5: Transplant the embryo to the uterus of the surrogate
mother ewe.
Fig.4(e) Roslin Technique
A clone
Step 6:
Allow the clone to give birth after the pregnancy period. The
clone have the same genetic makeup of the donor sheep.
Fig.4(f) Roslin Technique
The Honolulu technique
The new cloning technique, the Honolulu technique, was found to be more
efficient than that performed by Ian Wilmut in his cloning of Dolly. The Honolulu
technique was developed by Teruhiko Wakayama of the University of Hawaii and
used to genetically identical cloned mice. Unfertilized mouse egg cells were used as
the recipients of the donor nuclei, and after being enucleated, the donor nuclei were
inserted into the egg cells and then allowed to sit for an hour. Then, it is treated in a
chemical bath to active the cell for 5 hours just as fertilization does in nature.
As the cells develop into embryos, they are transplanted into surrogate
mothers and carried to term. The Honolulu technique was proved to be more efficient
than the Roslin technique, and had a higher success rate of 3 clones out of every 100
attempts, compared to that of the Roslin technique - 1 success out of every 277
attempts.
Wakayama also made clones of clones and allowed the original clones to give
birth normally to prove that they had full reproductive functions. Honolulu technique
resembles to the Roslin technique except the incubation time and type of cell used.
There is another difference in that the Roslin technique use electric shock to stimulate
egg development while the Honolulu technique use chemical bath. It is believed that
chemical bath is less destructive to the cell.
Unfertilised egg cell
Donor cell
Nucleus
Step 1: Remove the nucleus of an egg cell.
Fig. 5(a) Honolulu Technique
Egg cell without nucleus
Cumulus donor cell
Nucleus
S t e p 2 : I n t r o d u c e t h e c u m u l u s c e l l ( dl. o n o r c e l l ) i n t o t h e e g g c
Fig. 5(b) Honolulu Technique
Step 3:
Allow one hour for the egg cell to accept the donor cell.
Offer 5 more hours for the donor cell to fuse with the egg cell.
Fig. 5(c) Honolulu Technique
Egg cell with donor cell
Culture
(Containing cytochalasin B)
Step 4:
Place the cell in a culture solution for development into embryo.
The culture solution mimics the function of electric current.
Fig. 5(d) Honolulu Technique
Surrogate Mother
Developing Embryo
Step 5: Implant the embryo into the uterus of the surrogate sheep.
Fig. 5(e) Honolulu Technique
A clone
Step 6:
Allow the clone to give birth after the pregnancy period. The
clone have the same genetic makeup of the donor sheep.
Fig. 5(f) Honolulu Technique
Cloning had successfully done in animals, the same method can be applied to
humans. But cloning is a very delicate process and extreme care should be paid so as
to avoid any uncontrolled deviation.
Websites
Please refer to ‘Background Information for Teachers  References’.
Ethical, Legal and Social Implications of Cloning
Human Cloning
Human cloning can be subdivided into reproductive cloning and therapeutic
cloning. Reproductive cloning refers to the transfer of a somatic cell nucleus into an
enucleated egg in an effort to produce a child. Therapeutic cloning involves the
creation of embryos by nuclear transfer that can serve as a source of embryonic stem
cells for therapeutic application and treatment of degenerative disease in the somatic
cell donor. Reproductive cloning is subject to larger debate than the therapeutic
cloning as the former actually involve the production of new child.
What are the potential applications of human cloning?
Human cloning technology finds great application in medical science. It could
be used to reverse heart attacks. Scientists believe that they may be able to treat heart
attack victims by cloning their healthy heart cells and injecting them into the areas of
the heart that have been damaged.
There has been a breakthrough with human stem cells. Embryonic stem cells
can be grown to produce organs or tissues to repair or replace damaged ones (organ
farms). Skin cells, brain cells, heart cells, lung cells, liver cells, and kidney cells could
be produced. By combining this technology with human cloning technology it may be
possible to produce needed tissue for suffering people that will be free of rejection by
their immune systems. Conditions such as Alzheimer's disease, Parkinson's disease,
diabetes, heart failure, degenerative joint disease, and other problems may be made
curable if human cloning and its technology are not banned. The followings list more
specific applications of human cloning.
 Infertility - Human cloning could make it possible for many more infertile couples
to have children than ever before. Couples can thus avoid going through physically
and emotionally painful procedures in test-tube babies for just a small chance of
having children.
 Kidney failure - we may be able to clone kidneys for kidney transplants.
 Spinal cord injury - we may learn to grow nerves or the spinal cord back again when
they become injured. Quadriplegics will be possible to walk again without the use
of wheelchairs.
 Leukemia - cloning the bone marrow for children and adults can help those
suffering from leukemia.
 Cancer - we may learn how to switch cells on and off through cloning and thus be
able to cure cancer
What are the arguments against human cloning?
Ethics
The clone may face with the problem of who is her/his real parent. He or she
may have many quasiparents but none may take up the role of protector that a child’s
parents traditionally occupy. As a clone would be physically identical to their parent,
unbearable emotional pressures would be developed for a child to establish his or her
identity. In addition, cloning muddies the concepts of family e.g. a mother bears the
clone of her grandmother or his close relatives.
Health risks
Cloning is still a new technique. There exists mutation of genes that may
produce abnormal baby. Many attempts at animal cloning produced disfigured
monsters with severe abnormalities.
Risk of abuse of technology
It would be dangerous if the leader of a country abuses the technology for mass
production of clones not for the good of mankind but only for his own benefit.
Websites
Please refer to ‘Background Information for Teachers  References’.
References
Klotzko, A. J., (ed), The Cloning Source Book, Oxford University Press, 2001.
McGee, Glenn (ed), The Human Cloning Debate, Berkeley Hills Books, 2000.
Rollin, B. E., The Journal of Ethics, 3: 51-71, 1999.
B James A. Byrne and John B. Gurdon, “Commentary on human cloning”,
Differentiation 69:154-157, 2002.
Don P. Wolf, “ An opinion on human reproductive cloning”, Journal of Assisted
Reproduction and Genetics, Vol. 18, No. 8, 2001.
Websites

Basic Life Science Terms
“Microscopes, cells, DNA and you”
http://chroma.mbt.washington.edu/outreach/SUMMARY.html
“Genomics 101: The Basics”
http://www.ornl.gov/hgmis/publicat/primer2001/1.html
“How cell works – The cell part”
http://www.howstuffworks.com/cell1.htm

Cloning Techniques
“Human cloning – cloning methods”
http://www.stanfrod.edu/~eclipse9/sts129/cloning/methods.html
“Human cloning- how to do it”
http://www.globalchange.com/clone.html
“Human cloning – ways to clone”
http://www.stedwards.edu/newc/capstone/sp2000/biotechnology/ways.htm
“The Roslin Technique” and “The Honolulu technique”
http://library.thinkquest.org/24355/data/techniquesnav.

Ethical, Legal and Social Implications of Cloning
“The benefits of human cloning”
http://www.humancloning.org/benefits.htm
“All the reasons to clone human”
http://www.humancloning.org/allthe.htm