CLONING
(non-sexual/ asexual
reproduction)
INTRODUCTION
Cloning is a form of non-sexual/asexual
reproduction in which the offspring are
identical to the parent.
In nature many organisms clone by
themselves e.g. strawberry's have runners
in which the plant will grow from a stem
and the new plant will be identical to the
original plant.
CLONING FOR BUISNESS
New varieties of apple are developed by sexual
means from seeds and then the most
satisfactory types are simply cloned by
cuttings.
NATURAL CLONING
• Many organisms will clone naturally. Flowering
plants reproduce sexually by seeds but also
multiply by runners, suckers, tubers, bulbs, and
other structures that are just extensions of the
parent.
Mammals do sometimes clone naturally, but by a
different route. Sometimes a single embryo divides
in the womb to form identical twins, or even divides
twice to produce identical quads (four identical
babies). Nine-banded armadillos, for reasons
unknown, always produce identical quads. In such
cases, the offspring are clones of each other, but
are not clones of the mother.
IDENTICAL TWINS.
Identical Twins
These identical twins, separated at
birth, were reunited at the age of
31. Although raised apart, they had
a great deal in common. Both had
become firemen, wore moustaches,
were balding, had poor vision, and
enjoyed hunting and fishing.
Comparisons of twins reared apart
are one source of data for scientists
who wish to determine the relative
influence of heredity and
upbringing on particular traits.
SHEEP CLONING
• The cloning of sheep at Roslin Institute near Edinburgh
was a highly significant biological breakthrough, and one
of the most important scientific events of the 1990s. In
1995, Ian Wilmut, Keith Campbell, and their colleagues
cloned Megan and Morag from cultured embryo cells;
and in July 1996, Dolly, produced from cultured adult
cells, was born. In the following year, the biotechnology
company PPL (a research partner of Roslin) produced
Polly, who was not only cloned, but genetically
transformed (“engineered”). Polly had been fitted with a
human gene that causes her to secrete a human blood-
clotting factor in her milk, which potentially was of great
value to haemophiliacs.
PARTHENOGENISIS
One special form of asexual reproduction is
parthenogenesis, in which a new individual
develops from an unfertilized egg. Dandelions
and some other plants practice parthenogenesis,
and it also occurs in animals such as aphids,
some fish, some lizards, and even in some birds,
including some domestic turkeys. Again, the
parthenogenetic offspring and the parents
collectively form a clone. But it is possible to
reproduce parthenogentically without producing a
clone. Thus the male offspring of bees (the
drones) develop from unfertilized eggs but their
genes are recombined in the process so they are
not genetically identical to each other or to the
queen (who, of course, is female rather than
male). But this is a special case; typically the
products of parthenogenesis form a clone.
FUTRE OF CLONING
Yet, many have expressed concerns that these powerful
biotechnologies could be taken too far. Cloning of babies is certainly
likely and many regard this as dangerous. In February 2004 it was
announced in South Korea that human embryos had been created
by combining genetic material from non-reproductive (somatic) cells
and eggs from women donors. These cloned embryos were cultured
until they divided into all three of the main human tissue types; when
transplanted into mice they further differentiated into cells, showing
that cloned embryos could produce effective stem cells. In the
future, by using a patient’s own genetic material to clone stem cells
to produce transplantation material, it will be hoped that rejection by
the immune system will be avoided. It will also become possible to
change the genetic makeup of an embryo, eventually to the
possibility of the “designer baby”:
THE END
By Christine Hutchings