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The use of either embryo
splitting or nuclear replacement deliberately for the purposes
of human reproductive cloning, to produce genetically identical
human beings, raises serious ethical issues, concerned with human
responsibility and instrumentalisation of human beings.
Cloning by
embryo splitting would artificially reproduce the natural process
by which identical twins, who make up approximately one third
of twins in the UK, are produced. World-wide, there are approximately
3-4 monozygotic twinnings per 1000 births. Such naturally occurring
twins show that genetically identical individuals are far from
being identical people: they may differ from one another physically,
psychologically, in personality and in life experience. The intrauterine
environment may cause lasting differences. It is reported that
some monozygotic twins have problems in establishing their identity
and experience delayed language development and problems forming
other relationships. It is also reported that these difficulties
usually arise when the children have been treated as an indistinguishable
and inseparable pair. If individual humans were cloned by nuclear
replacement from an adult cell, they would, of course, be even
more different from their donor, since their mitochondria, their
age, their environment, both before and after birth, and their
upbringing would differ. 
The
experience of natural identical twins suggests that a unique genetic
identity is not essential for a human being to feel, and be, individual(14).
Therefore what is meant by the assertion that individuals have
the right to their own genetic identity? What does this mean for
identical twins?
Lee
M. Silver
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