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

Abstract: This review describes the manipulation of the sheep genotype by
genetic engineering, which is defined as the introduction or elimination of
specific genes in the existing cells of an organism through modern biological
techniques for the purpose of changing one or more of its phenotypic
characteristics. This can be achieved by direct injection of a DNA sequence
for a gene or gene-related function or by transfer of an intact nucleus from a
somatic cell containing a set of desirable genes into an enucleated egg cell.
The potential of transgenesis over conventional breeding is that single gene
changes can be made for a particular phenotype without accompanying
multiple gene effects that can be disadvantageous. Several examples of
engineered sheep are described. The potential for making other transgenic
changes are discussed but transgenic sheep research has virtually ceased
because of high cost and the perceived low public acceptance of transgenic
animals at the present time.
Key words: wool properties, genetic engineering, gene transfer, transgenesis,
wool keratin.