In biology, cloning is the process of
producing similar populations of genetically identical individuals that occurs
in nature when organisms, such as,
bacteria, insects or plants reproduce asexually.
The cloning of plants is a common practice of
mankind since the 5000 BC while the cloning of animals has been dated back to
the 1960s. However, the idea of human cloning has not been thought possible
until the successful cloning of the first mammal – Dolly, the sheep, 1997.
After the cloning of Dolly, several other mammals such as mice and cows have
been successfully cloned. Here is a timeline that shows the history of cloning.
Timeline of cloning:
5000 BC – Humans have discovered that to improve
the quality of their crops from the best plants.
1866 – George Mendel published “Experiments in
Plant Hybridization” which established the basic laws of inheritance, making
him known as the “Father of Genetics”.
1869 – DNA from the nuclei of white blood cells
is extracted.
1880s – August Weissmann states genetic information
of a cell
would diminish with each cell division.
Wilhelm Roux confirmed Weismann's theory when he destroyed one cell of a
2-cell frog embryo with a hot needle and only a half-embryo developed.
1902 - Walter Sutton, in "On the Morphology
of the Chromosome
Group in Brachyotola magna", hypothesized that chromosomes hold the
genetic information in the nucleus.
1914 – Hans Spemann performed the first successful
near transfer experiments.
1938 – Spemann proposed a “fantastical
experiment” to transfer one cell’s nucleus into a egg without a nucleus,
providing the basis for subsequent cloning experiments.
1962 - John Gurdon of Oxford University claimed
that he had cloned South African frogs from the nucleus of fully differentiated
adult intestinal cells.
1969 - James Shapiero and Johnathan Bechwith of
Harvard University isolated the first gene and led to the growing power of
molecular biologists.
1984 - Steen Willadsen cloned a sheep from
embryonic cells. This was the first confirmed case of mammalian cloning by
nuclear transfer.
1986 - Steen Willadsen cloned a cow by using differentiated cells extracted from one-week-old embryos.
1986 - Neal First, Randal Prather, and Willard
Eyestone of the University of Wisconsin also cloned a cow from embryonic cells.
1990 – Start of the Human Genome Project, an
international scientific research project that aims to determine the sequence
of chemical base pairs which make up human DNA and also to identify and map the
total genes of the human genome from both a human and functional standpoint, it
is the largest collaborative biological project.
1996 - Ian Wilmut and Keith Campbell cloned the
first animal, Dolly the sheep, from adult cells. The cloning of Dolly is one of
the most important milestones in the history of animal cloning proving the possibility of cloning adult
animals.
1998 – Dolly the sheep gave birth to 3 healthy
lambs, which were conceived by natural mating.
2001 - Scientists at Advanced Cell Technology,
Inc. announced the birth of a cloned baby bull gaur called Noah, the first
endangered animal to be cloned. Although Noah died of an infection unrelated to
the cloning procedure, the experiment opened the door to saving endangered
species through cloning.
