By: Dean Aszman, Nishit Patel, Jonathan Pekar, and Robby Lancaster
Table Of Contents
History of Cloning
Timeline Of Cloning
History of Cloning
Cloning is not new. Experiments with frogs and toads date back to the
1970s . And experiments involving plants and animal embryos have been
performed for years. But experiments involving human beings have never
been tried or thought possible, until "Dolly." Her birth shocked the
scientific community and has spurred discussion about the possibility of
human clones. Dr. Lee Silver, a molecular biologist at Princeton University,
is optimistic that "human cloning will occur," and that "it might take five
years, ten years at the outermost." Lee notes that at this time, "no ethical
doctor would do human cloning“.Although this view is predominant
among many scientists, some argue that a safe technology could be
developed in the future. This has led to discussion about whether human
cloning should even be legally possible.
Reproductive cloning is a technology used to generate an animal that has
the same nuclear DNA as another currently or previously existing
animal. Dolly was created by reproductive cloning technology. In a
process called "somatic cell nuclear transfer" (SCNT), scientists
transfer genetic material from the nucleus of a donor adult cell to an
egg whose nucleus, and thus its genetic material, has been removed.
The reconstructed egg containing the DNA from a donor cell must be
treated with chemicals or electric current in order to stimulate cell
division. Once the cloned embryo reaches a suitable stage, it is
transferred to the uterus of a female host where it continues to
develop until birth.
Therapeutic cloning, also called "embryo cloning," is the production of human
embryos for use in research. The goal of this process is not to create cloned
human beings, but rather to harvest stem cells that can be used to study
human development and to treat disease. Stem cells are important to
biomedical researchers because they can be used to generate virtually any
type of specialized cell in the human body. Stem cells are extracted from the
egg after it has divided for 5 days. The egg at this stage of development is
called a blastocyst. The extraction process destroys the embryo, which raises
a variety of ethical concerns. Many researchers hope that one day stem cells
can be used to serve as replacement cells to treat heart disease, Alzheimer's,
cancer, and other diseases.
In November 2001, scientists from Advanced Cell Technologies (ACT), a
biotechnology company in Massachusetts, announced that they had cloned the
first human embryos for the purpose of advancing therapeutic research. To do
this, they collected eggs from women's ovaries and then removed the genetic
material from these eggs with a needle less than 2/10,000th of an inch wide. A
skin cell was inserted inside the enucleated egg to serve as a new nucleus. The
egg began to divide after it was stimulated with a chemical called ionomycin.
The results were limited in success. Although this process was carried out with
eight eggs, only three began dividing, and only one was able to divide into six
cells before stopping.
DNA cloning is the transfer of a DNA fragment from one organism
to a self duplicating element such as a bacterial plasmid
Scientists studying a particular gene often use bacterial plasmids
to create copies of a type of gene
Plasmids are self
duplicating extra chromosomal circular DNA
To duplicate a gene, a DNA fragment of that gene is taken as a
sample, or removed, from chromosomal DNA using restriction
enzymes and then combined with a plasmid that has already been
taken by the same restriction enzymes
Pros and Cons of Cloning
There is no better way to
understand the human genome
Ability to produce
Medical methods will be
boosted by generations
More elaborate understanding
of our past
There will be no more of a wait
for organ transplants
Humans are not made to be
guinea pigs and they are of free
Ability to produce
Countries could clone armies
If humans can be cloned then
they can be sold, which is
If everyone has the same
genotype, then a fatal disease
that only effects that genotype
could wipe out the human race
August Weismann, professor of zoology and comparative anatomy at
the University of Freiberg, theorized that the genetic information of a
cell would diminish as the cell went through differentiation.
Wilhelm Roux tested the germ plasma theory for the first time. One
cell of a 2
cell frog embryo was destroyed with a hot needle; the
result was a half
embryo, supporting Weismann's theory.
Hans Dreisch isolated blastomeres from 2
cell sea urchin
embryos and observed their development into small larvae. These
experiments were regarded as refutations of the Weismann
Hans Spemann split a 2
cell newt embryo into two parts, resulting in
the development of two complete larvae.
Timeline Of Cloning
German embryologist Hans Spemann split a 2
celled salamander embryo and
each cell grew to adulthood, providing proof that early embryo cells carry
necessary genetic information. This finally disproved Weismann's 1885 theory
that the amount of genetic information in cells decreases with each division.
Hans Spermann conducted and early nuclear transfer experiment.
Hans Spemann performed further, successful nuclear transfer experiments.
Hans Spemann published the results of his 1928 primitive nuclear transfer
experiments involving salamander embryos in the book "Embryonic
Development and Induction." Spemann argued the next step for research
should be the cloning organisms by extracting the nucleus of a differentiated
cell and putting it into an enucleated egg.
Oswald Avery found that a cell's genetic information was carried in DNA.
First successful freezing of bull semen at
C for later insemination of cows
First animal cloning: Robert Briggs and Thomas J. King cloned northern leopard
Francis Crick and James Watson ,working at Cambridge's Cavendish Laboratory,
discovered the structure of DNA.
Paul Berg combined the DNA of two different organisms, thus creating the first
recombinant DNA molecules.
Stanley Cohen and Herbert Boyer created the first recombinant DNA organism
using recombinant DNA techniques pioneered by Paul Berg. Also known as gene
splicing, this technique that allows scientists to manipulate the DNA of an
the basis of genetic engineering.
Karl Illmensee and Peter Hoppe created mice with only a single parent.
David Rorvik published the novel
In His Image: The Cloning of a Man
Baby Louise, the first child conceived through
fertilization, was born.
Karl Illmensee claimed to have cloned three mice.
In the case Diamond v. Chakrabarty, the United States Supreme Court ruled
that a "live, human made microorganism is patent able material."
Kary B. Mullis developed the polymerize chain reaction (PCR) in 1983. This
process allows for the rapid synthesis of designated fragments of DNA.
Davor Solter and David McGrath tried to clone mice using their own version of
the nuclear transfer method.
The first human mother
mother embryo transfer was completed.
Marie A. Di Berardino, Nancy H. Orr, and Robert McKinnell transplanted nuclei of
adult frog erythrocytes, thus obtained pre
feeding and feeding tadpoles.
Steen Willadsen cloned a sheep from embryo cells, the first verified example of
mammal cloning using the process of nuclear transfer.
able to break down and be reabsorbed by the environment
the basic building block of life
the structure that contains genes DNA
an organism that has the same genes as another organism
using genes to make a copy of an organism
a chemical substance that give instructions to cells
a tool used to study extremely small objects such as cells and genes
a section of DNA that passes traits from parent to offspring
tests to find damage or missing genes
using genetic engineering to fight or cure a disease
placing a section of DNA from one organism to another
The study of genes, DNA, and heredity
The passing of traits from parent to offspring
the outer part of a cell
a pouch inside the cell that contains the DNA
We think that there should not be human cloning. It would be
inhumane because they become slaves to us. Also, if everyone
made clones eventually we would all have the same genotype. Wars
could never end because both sides would keep cloning their
armies. And once we all have one genotype, there may be disease
that are fatal to this genotype. The only good thing about cloning is
that we would always be able to make an organ if somebody needs
an organ transplant.
Life in the Future: Cloning and Genetic Engineering; 2002; by Holly Crefey