Formulae on Principles Of Inheritance And Variation

Pedigree analysis is a diagrammatic illustration depicting the passage of a certain trait through successive generations in a family lineage. It helps in genetic counseling.

Genic interaction manifests in modified ratios of phenotypic segregation in the F2-genertion of dihybrid crosses. Notable modified dihybrid ratios include 9 : 7 (for complementary genes), 13:3/12:3:1 (for epistasis , also referred to as dominant epistasis; please note that the concept of recessive epistasis that could produce a ratio of 9:3:4, like that for supplementary genes, has been proved absurd/wrong since long), 15 : 1 (for duplicate genes), and 9 : 3 : 4 (for supplementary genes).