When an embryo is created by nuclear transfer and implanted into a surrogate
mother in the hope of bringing it to term, this process is called reproductive
cloning. It means creating a new individual from a single cell by replacing
the nucleus in an egg cell with the nucleus (containing the genetic material)
from another cell of the body. When the cloned egg cell grows and develops into
an embryo, it is implanted inside a surrogate mother's womb to mature and produce
a viable fetus. After birth, the clone would, in theory, be a genetic copy of
the adult whose nucleus was used for cloning.
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So far, the reproductive cloning performed in animals
has been fraught with biological and technical problems. Only about
1% of all the eggs that receive donor DNA can develop into normal surviving
clones. And, the clones that survive often develop many health problems.
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