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Limitations
of Cloning 1: Genetic Defects & Gender
A
clone will be identical to the genetic parent
(tissue donor). It will be the same sex and it
will have the same genetic defects or mutations
which were present in the tissue donor. Genetic
research is advancing so that one day genetic
defects might be weeded out of individual cells
and healthy genes inserted instead (e.g. using a
virus to carry healthy genes into the cell) but at
present the clone will be as healthy or as
unhealthy as the tissue donor.
Cloning relies on the fact that all cells
contain the instructions for making a whole body.
For example, in its DNA a skin cell contains the
instructions for making an eye. In the normal run
of things, the skin cell doesn't make eyes so if
something goes wrong with its copy of the
"make eye" genes (e.g. damage from
sunlight or chemicals) it is not disastrous,
because the skin cell is making skin cells (which
will inherit the damaged "make eye"
genes) and not eyes. However, if that skin cell is
used to make a clone, the clone will inherit
damaged "make eye" genes. Something will
go wrong with the formation of eyes in the embryo.
In the normal run of things, an embryo inherits
a set of genes from each parent, giving it a
"back-up" copy if any genes are damaged
or defective. It is very bad luck if both copies
of a particular gene are defective. In a clone,
there are no back-up copies of genes. Localized
damage in the donor cell are passed on to the
clone.
The older the donor, the more likely there
is to be damage. Though the damage might be
invisible in the donor cell, it could be
disastrous in the clone. This may be why so many
attempts at cloning produce defective embryos -
they are being made from cells with damaged DNA.
The damage will show up when the cell tries to run
certain instructions which it would not normally
run when doing its normal function (e.g. being
skin).
The clone will be the same as the original was
before any accident, illness or surgery. If the
original was neutered, the clone will be
unneutered because "acquired traits"
(things done to the animal during its life) cannot
be inherited. The only exceptions to this is cell
mutations caused by cell poisons or radiation;
clones made from radiation-damaged cells will be
equally damaged because the DNA itself has been
damaged.
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