Theory for the number of genes affecting quantitative characters

Abstract

Current methods for the detection of loci affecting quantitative characters in Drosophila may be in error in two ways, (i) The detection of loci which do not exist. (ii) The magnification of the estimated effect of those major loci which do exist by accumulating to their effect those of undetected loci close to them on the chromosome. This paper considers the magnitude of the second type of error and shows that the estimates of the effect of major loci may be too high by up to five times the standard error of measurement of each cross-over chromosome examined.

Estimation of the number of loci involved in the inheritance of resistance to Phytophthora palmivora (Butl.) Butl. in the leaves of Theobroma cacao L.

“…The low environmental component of variation under the experimental conditions described here made the study of resistance traits in T. cacao suitable for gene number estimates. These arc considered more reliable when heritability is high (Park, 1977). For a tree species, this method of gene number estimation had considerable advan-tages over those described by Wright (1968) and Mather & Jinks (1971) in not requiring either long-term selection experiments or inbred lines.…”

“…Comparisons of theoretical and observed progeny distributions were used to estimate the minimum number of loci affecting the components of resistance (Park, 1977). It was assumed that the theoretical distribution of progeny phenotypes was caused solely by the segregation of n unlinked heterozygous loei.…”

Parâmetros genéticos e fenotípicos da resistência a >i<Exserohilum turcicum>/i< (Pass.) Leonard & Suggs em populações de milho

“…Na prática geralmente uma ou mais destas suposições não são cumpridas obtendo-se estimativas de pouca confiabilidade (TANKSLEY, 1993). Vários métodos têm sido propostos para estimar o número de genes (CASTLE, 1921;JINKS & TOWEY, 1976;PARK , 1977)…”