Cloning of Mammals – Biological Aspects

Overview

Cloning by somatic cell nucleus transfer into enucleated oocytes represents a very straightforward approach. Thenucleus is simply transferred into the oocyte from which its nuclear genetic material (chromosomes) has been earlierremoved.By using this approach clones of sheep, cattle, horse, rabbit, goat, rat,mule, pig, cat and interspecies-specificclone mouflon x sheep were obtained. The success of cloning is, however, disappointingly low and only 1–3 % ofreconstructed embryos develop to term. Some cloned animals are abnormal and die prematurely. This clearly speaksagainst the use of cloning in humans. On the other hand, so called therapeutic cloning, when the nucleus is transferredinto an oocyte and the developing embryo is then used for the production of embryonic stem cells is generally wellaccepted. This promising techniqe may be probably used in some as yet untreatable diseases and in certain seriousinjuries.

Key words:
cloning, nucleus, oocyte, embryonic stem cells.