Information excerpted from:
How Cloning Works
How Human Cloning Will Work
by Craig Freudenrich, Ph.D.
by Kevin Bonsor and Cristen Conger
http://science.howstuffworks.com/life/genetic/cloning.htm
Animal cloning has been the subject of scientific experiments for years, but
garnered little attention until the birth of the first cloned mammal in 1996, a sheep
named Dolly.
Stephen Ferry/Getty Images
Introduction to How Cloning Works
On Jan. 8, 2001, scientists at Advanced Cell Technology, Inc., announced the birth
of the first clone of an endangered animal, a baby bull gaur (a large wild ox from
India and southeast Asia) named Noah. Although Noah died of an infection
unrelated to the procedure, the experiment demonstrated that it is possible to save
endangered species through cloning.
Cloning is the process of making a genetically identical organism through
nonsexual means. It has been used for many years to produce plants (even growing
a plant from a cutting is a type of cloning).
Animal cloning has been the subject of scientific experiments for years, but
garnered little attention until the birth of the first cloned mammal in 1996, a sheep
named Dolly. Since Dolly, several scientists have cloned other animals, including
cows and mice. The recent success in cloning animals has sparked fierce debates
among scientists, politicians and the general public about the use and morality of
cloning plants, animals and possibly humans.
Why Clone?
The main reason to clone plants or animals is to mass produce organisms
with desired qualities, such as a prize-winning orchid or a genetically engineered
animal -- for instance, sheep have been engineered to produce human insulin. If
you had to rely on sexual reproduction (breeding) alone to mass produce these
animals, then you would run the risk of breeding out the desired traits because
sexual reproduction reshuffles the genetic deck of cards.
Other reasons for cloning might include replacing lost or deceased family
pets and repopulating endangered or even extinct species. Whatever the reasons,
the new cloning technologies have sparked many ethical debates among scientists,
politicians and the general public. Several governments have considered or
enacted legislation to slow down, limit or ban cloning experiments outright. It is
clear that cloning will be a part of our lives in the future, but the course of this
technology has yet to be determined
Introduction to How Human Cloning Will Work
On July 5, 1996, the most famous sheep in modern history was born. Ian Wilmut
and a group of Scottish scientists announced that they had successfully cloned a
sheep named Dolly.
If you stood Dolly beside a "naturally" conceived sheep, you wouldn't
notice any differences between the two. In fact, to pinpoint the only major
distinguishing factor between the two, you'd have to go back to the time of
conception because Dolly's embryo developed without the presence of sperm.
Instead, Dolly began as a cell from another sheep that was fused via electricity
with a donor egg. Just one sheep -- no hanky-panky involved.
While Dolly's birth marked an incredible scientific breakthrough, it also set
off questions in the scientific and global community about what -- or who -- might
be next to be "duplicated." Cloning sheep and other nonhuman animals seemed
more ethically benign1 to some than potentially cloning people. In response to
such concerns in the United States, President Clinton signed a five-year
2
moratorium on federal funding for human cloning the same year of Dolly's
arrival [source: Lamb].
Today, after more than a decade since Dolly, human cloning remains in its
infancy. Although cloning technology has improved, the process still has a slim
success rate of 1 to 4 percent [source: Burton]. That being said, science is headed
in that direction -- pending governmental restraints.
Scientists have cloned a variety of animals, including mice, sheep, pigs,
cows and dogs. In 2006, scientists cloned the first primate embryos of a rhesus
1
2
Benign = less dangerous
Moratorium = an order
which temporarily forbids an activity
monkey. Then, in early 2008, the FDA officially deemed milk and meat products
from cloned animals and their offspring safe to eat.
Creating a Human Clone
In January 2001, a small group of scientists led by Panayiotis Zavos, a
former University of Kentucky professor, and Italian researcher Severino Antinori
said that they planned to clone a human in two years [source: Kirby]. At about the
same time, news surfaced about an American couple who planned to pay $500,000
to Las Vegas-based company Clonaid for a clone of their deceased infant daughter
[source: Clonaid]. Neither venture produced documented success.
Then, in 2004, South Korean scientist Hwang Woo-suk announced that he
and his research team had cloned 11 human embryos for the purpose of
extracting3 stem cells. However, after reviewing his work, a panel at Seoul
National University concluded that his findings were false. There hasn't been any
confirmed human clone created to date. When discussing cloning in the sense of
doing so to make a duplicate of an organism, we refer to it as reproductive cloning.
If human reproductive cloning proceeds, the primary method scientists will likely
use is somatic cell nuclear transfer (SCNT), which is the same procedure that was
used to create Dolly the sheep. Somatic cell nuclear transfer begins when doctors
take the egg from a female donor and remove its nucleus, creating an enucleated
egg. A cell, which contains DNA, is taken from the person who is being cloned.
Then the enucleated egg is fused together with the cloning subject's cell using
electricity. This creates an embryo, which is implanted into a surrogate mother
through in vitro fertilization.
Figure 1: Somatic Cell Nuclear Transfer
Figure taken from http://www.biotechnologyonline.gov.au/popups/img_scnt.html
3
Extracting = removing
Cloning Uses
At the beginning of the clone craze, some scientists and companies focused
on marketing the science-fiction aspects of the technology. For instance, Zavos
and Antinori, mentioned earlier, aimed to develop cloning to aid infertile couples - to the tune of approximately $50,000 for the service. The group said that the
procedure would involve injecting cells from an infertile male into an egg, which
would be inserted into the female's uterus. This child would look the same as his
or her father. Then there's the possibility of bringing deceased relatives back to
life. A now-nonexistent company called Genetics Savings & Clone performed this
type of cloning for a woman's dead cat, Little Nicky, in 2004.
Therapeutic cloning 4holds the most promise of valuable medical
advancement. Therapeutic cloning is the process by which a person's DNA is used
to grow an embryonic clone. However, instead of inserting this embryo into a
surrogate mother, its cells are used to grow stem cells. These stem cells could
become the basis for customized human repair kits. They can grow replacement
organs, such as hearts, livers and skin. They can also be used to grow neurons to
cure those who suffer from Alzheimer's, Parkinson's or Rett syndrome. And since
the stem cells would come from embryo clones using your own cell's DNA, your
body would readily accept them.
Human Cloning Ethics
Surveys have shown that few Americans approve of cloning for
reproductive purposes (i.e., for the purposes of having children who are
genetically your own/have certain desirable traits, etc.), although more are open to
therapeutic cloning [source: Burton]. The U.S. government has established
strategic roadblocks related to human cloning, although no federal ban exists.
First, the government won't fund research focused on human cloning for
reproduction. Also, the FDA, which regulates public cloning research, requires
anyone in the United States attempting to clone humans to first get its permission.
President George W. Bush's appointed Council on Bioethics unanimously opposed
cloning for reproductive purposes.
Certain countries abroad have stricter standards, and more than 50 have legally
banned research efforts on reproductive human cloning [source: Medical Devices
& Surgical Technology]. In Japan, human cloning is a crime punishable by up to
10 years in prison. England has allowed cloning human embryos for therapeutic
use only. Many individual states have also passed laws restricting cloning.
While legal restrictions are one deterrent to pursuing human cloning at this
time, some scientists believe today's technology just isn't ready to be tested on
humans. Ian Wilmut, one of Dolly's co-creators, has even said that human cloning
projects would be irresponsible. Cloning technology is still in its early stages, and
4
Cloning used to help cure people of diseases. In this article, it refers to growing organs for use in organ
transplants.
nearly 98 percent of cloning efforts end in failure. The embryos are either not
suitable for implanting into the uterus, or die some time during gestation or shortly
after birth.
Those clones that do survive suffer from genetic abnormalities. Clone cells
may age more rapidly, shortening their lifespan, similar to what happened with
Dolly. Some clones have been born with defective5 hearts, lung problems,
diabetes, blood vessel complications and immune systems that don’t work right.
One of the more famous cases involved a cloned sheep that was born but suffered
from chronic hyperventilation caused by badly formed arteries leading to the
lungs.
Opponents of cloning point out that while we can 6euthanize defective
clones of other animals, it's morally problematic if this happens during the human
cloning process. Advocates of cloning respond that it's now easier to pick out
defective embryos before they're implanted into the mother. In 2005, the United
Nations attempted to pass a global ban on human cloning, but was unsuccessful
due to disagreements over whether therapeutic cloning should be included. For
now, human cloning remains in a 7stalemate from both a scientific and public
policy perspective -- the future of human cloning will likely depend on which side
gives in first.
5
Defective = unusable for the long-term; fawlty
Euthanize = put to sleep (as one does with old dogs and cats)
7
Stalemate = deadlock/unbreakable tie. Neither side is winning and neither side is willing to compromise
so there is no movement at all.
6
Name ______________
Date ______________
Period ___________
Guided Notes: Excerpts from “How Cloning Works” by Craig Freudenrich, Ph.D. and “How Human Cloning Will Work” by Kevin
Bonser and Cristen Conger
Introduction to How Cloning Works
Focus Question: What is cloning? What does that word mean? When was the first animal cloned?
Cloning is defined as __________________________________ ______________. Ever the since the cloning of __________ in
1996, scientists have debated the morality of cloning several different types of animals as well as humans.
Why Clone?
Focus Question: How do humans use animal cloning to their advantage?
Some reasons mentioned in this sections that humans might benefit from cloning animals are:
Creating a Human Clone
Focus Question: What is the process called that would be used to clone humans? How does it work?
The process that would be used to clone humans is called _________________________________.
Cloning Uses
Focus Question: What are some ways humans might think it helpful to clone humans?
Some uses for human cloning might be:
A. ____________________________________
B. ____________________________________
C. ____________________________________
Human Cloning Ethics
Focus Question: Why do some people say we should not clone humans (or at least, not clone them right now?) Why do others
say now is a good time to clone?