O o d h e a d p u b L i s h I n g L i m I t e d

1.1
Introduction
Over many decades remarkable improvements in wool production in terms
of quality (diameter, length, staple strength, crimp and colour) and yield
(rate of wool growth) have been achieved through selective breeding and
nutrition. Sheep breeding methodologies can be regarded as genetic engineering
and will undoubtedly be of benefit in the future through the advent of genome
characterisation and gene discovery that will provide molecular markers for
more accurate selection of sheep and wool characters. The term genetic
manipulation used in the present discussion is usually referred to as genetic
engineering and is defined as the introduction or elimination of specific
genes in the existing cells of an organism through modern molecular biology
techniques for the purpose of changing one or more of the organism’s
phenotypic characteristics. This can be achieved by direct injection of a
DNA sequence characterised for a gene or gene-related function into a fertilised
egg (transgenesis) or by transfer of an intact nucleus from a somatic cell
containing a set of desirable genes into an enucleated egg cell, a process that
yields an animal clone, or by variations of these. The potential advantage of
© 2009 Woodhead Publishing Limited

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Advances in wool technology
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transgenesis is that single gene changes can be made rather than selectively
breeding sheep for a particular phenotype, in which case there are accompanying
multiple gene effects that can be disadvantageous.
This review describes the manipulation of the sheep genotype by these
procedures, utilising tested and prospective genes for improving aspects of
wool growth and wool quality, and some of the problems to be confronted.