Abstract

This paper will not deal with breeding for qualitative traits (such as use of 
sexlinked genes for chick sexing, or breeding for homogeneity of color or mor
phological characters, etc...). It will concerne possible utilization of identi
fied genes, considered as qualitative genetic units, as an aid to selection for 
quantitative traits

Till now, very few single gene effects have been really taken into account in 
practical breeding. In the past, elimination of male infertility associated with 
Rose Comb in the White Wyandotte can be regareded as an example. Later, intro
duction of the sex-linked dwarf gene in broiler female strains is another one. 
Anyway, a widespread opinion is that the integration of mendelian factors in 
breeding programs is not in fact a practical problem, owing to its rarity. It is 
true that at present identified genes represent a very small part of the whole 
genome. Moreover, as has been stressed (ROBERTSON, 1970), it is likely that in 
populations selected since many generations genes with considerable individual 
effect on quantitative traits have already been most often fixed at the homozy
gous state.

P. Merat

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 5. Plenary sessions, , 727–741, 1982