the quantitative traits, however,are economically important measurable phenotypic traits of degree such as height, skin pigmentation, susceptibility to pathological diseases or intelligence in man; amount of flowers, fruits, seeds, milk, meat or egg produced by plants or animals, etc. The quantitative traits are also called metric traits are also called metric trait. They do not show clear cut differences between individuals and forms a spectrum of phenotypes which blend imperceptively from one type to another to cause continuous variations. In contrast to qualitative traits, the quantitative traits may be modified variously by the environmental conditions and are usually governed by many factors or genes, each contributing such a small amount of phenotype that their individual effects cannot be detected by Mendelian methods but by only statistical methods.