Cloning
Cloning
is the process of producing similar populations of genetically identical
individuals that occurs in nature when organisms such s bacteria insects or
plants reproduce asexually. You might also know it as mitosis, but this refers
only to the natural process by which eukaryotic cells split and reproduce to
create genetically identical offspring. It is extremely simple for scientist to
clone organisms that are unicellular (bacteria, yeast) however the cloning of
stem cells proves to be far more complicated and challenging.
The
cloning of stem cells is also known as somatic-cell nuclear transfer (SNCT) and
it involves creating embryos, not for the purpose of creating cloned humans but
to harvest the steam cells for further research on human development. Some form
of a cloned human has been made in the past, but its cell did not divide enough
times to develop properly. It is believed that human clones have been created
and hidden from the press, however officially human stem cell lines have not
yet been isolate from a clonal source. Cloning can also be a form of therapy as
embryonic stem cells can be harvested to treat diseases like diabetes and
Alzheimer’s. The process of cloning involves removing the nucleus from an egg
cell and taking the nucleus from an adult cell and inserting it in to the egg
cell. The egg reacts with the new nucleus and begin to develop in to an embryo
which will then become a blastocyst and further have the ability to become any
human cell. The SNCT process is common because it is genome-specific and the
scientists can exclude certain traits, which they do in practice for farm
animals. The most challenging step in SNCT is once the somatic cells have been
acquired, the maternal DNA must be removed from the oocyte while it is in Metaphase
II. After this has been done the somatic nucleus is introduced and the one-cell
embryo can develop. If the embryo is successfully developed it is inserted in a
surrogate (cow or sheep if it is a farm animal).
Cloning
has come a long way since the famous sheep Dolly, who was a clone in 1996, when
only one out of 277 eggs survived the process of SNCT. Nowadays, researchers
are able to successfully clone seven to eight out of ten eggs and a Korean
company (Sooam Biotech) is known to produce 500 cloned embryos a day. There
remains a lot of ethical debate as to wether cloning should be allowed or not,
it is common in farm animals and plants yet it remains illegal to clone human
embryos beyond 8 days.
ETR
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