Cloning Facts
What is Cloning? Cloning is the production of one or more individual
plants or
animals that are genetically identical to another plant or animal.
Nature itself
is the greatest cloning agent. In about one of every 75 human
conceptions, the
fertilized ovum splits for some unknown reason and produces
monozygotic
(identical) twins. Each has a genetic makeup identical to the
other. Two very
different procedures have been referred to as "cloning": ·
Embryo
cloning has been successfully carried out for years on many species of
animals.
Some limited experimentation has been done on human embryos. ·
Adult DNA
cloning has been used to clone a sheep, but was not tried on humans
until
December 1998. How is Embryo Cloning is Done? Human embryo cloning
starts with a
standard in vitro fertilisation procedure. Sperm and an egg
cell are mixed
together on a glass dish. After conception, the zygote
(fertilised egg) is
allowed to develop into a blastula (a hollow mass of
cells). The zygote divides
first into two cells, then four, then eight... A
chemical is added to the dish
to remove the "zona pellucida" covering. This
material provides
nutrients to the cells to promote cell division. With the
covering removed, the
blastula is divided into individual cells, which are
deposited on individual
dishes. They are then coated with an artificial zona
pellucida and allowed to
divide and develop. The experiment by Sillman showed
that the best results could
be obtained by interrupting the zygote at the
two-cell stage. Many of these
pairs of zygotes were able to develop to the
32-cell stage, but no further. They
might well have had the potential to
develop further and even mature into a
viable foetus, except that the
original ovum was defective and would have died
anyway. For ethical reasons,
the researchers selected embryos which had no
possibility of ever maturing
into foetuses, and thus into newborn babies. How is
Adult DNA Cloning
Done? With the exception of the sperm and egg, every cell in
the body
contains all of the genetic material in its DNA to theoretically create
an
exact clone of the original body. But cells have been
"biochemically
programmed to perform limited functions." The other functions
are turned
off. Most scientists had believed that such differentiated cells
could not be
reprogrammed to be capable of behaving as a fertilized egg. In
the case of the
sheep "Dolly", a cell was taken from mammary tissue of a
mature 6 year
old sheep while its DNA was in a dormant state. It was fused
with a sheep ovum
which had had its nucleus removed. The "fertilised" cell
was then
stimulated with an electric pulse. Out of 277 attempts at cell
fusion, only 29
began to divide. These were all implanted in ewes. 13 became
pregnant but only
one lamb, Dolly, was born. History of Cloning Cloning has
had a fairly long
history: · The first successful cloning experiment involved
a leopard frog. It
took place in, 1952 with group of scientist from the
Institute for Cancer
Research in Philadelphia. To clone the frog they
used an embryonic frog cell
nucleus · In 1962, John Gurdon of Cambridge
University cloned a toad that
survive threw adulthood and was able to
reproduce. He was also the first to take
a nucleus from a fully contrast
tadpole intestinal cell and cloned
toads(Robertson) · In 1981, Steen
Willadsen was the first to clone an
artificial chimera. He did this by mixing
a sheep and a goat getting the result
of a "geep". It had the body shape and
the head of a goat, and a
dappled coat which had large patches of sheep's
wool · In 1984, Willadsen
cloned the first verifiable mammal, using embryonic
nuclei transplant into an
unfertilised sheep egg · In 1986, when Willadsen
worked for Texas
bioengineering company, he produced the first cloned calves
from cattle by using
the embryonic nuclei. The cloned cattle that were
produced were super-elite,
high production dairy cows and bulls who had a
high breeding rate · In 1987,
James Robl of the University of
Massachusetts was the first to clone rabbits
also using embryonic nuclei
Going by these past events, who can say when we will
be able to clone human
organs or complete "biocopies" of human beings
by using just the nuclei taken
from a skin sample. Advantages and Disadvantages
Cloning has many more
advantages than disadvantages. Through cloning, you could
help thousands of
people and animals. Some of the ways that people could be
helped are: ·
Totally reduce organ donor lists · Bring back endangered species
· Allows
dairy products to be enriched. For example, cloning provides
scientists a
method to engineer cows to produce certain medicines or enzymes in
there milk
· Cure life threatening diseases and repair cosmetic defects ·
Produce
new, fresh tissue for burn victims, or new nerve tissue for burns or
back
injuries · Produce new heart cells for people with bad hearts There are
also
disadvantages of cloning, they are: · Taking God’s work into our own
hands ·
Have an impact on the decline in genetic variety · If we ever lost
the
ability to clone, we would have to resort to natural reproduction,
causing us to
inbreed, which could be disastrous · If everyone had the same
genetic
information, one disease could wipe out a whole population.