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 Godís 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.