Principles of Genetics and Breeding

2.1.7 Back cross and Test cross

To know whether F₁ and F₂ offsprings showed dominant characters were homozygous or heterozygous, Mendel carried out Back cross.

• When F₁ individuals are crossed with one of the two parents then such a cross is called as Back cross.
• When F₁ is back crossed with its recessive parent,it is called Test cross.
• When F₁ is backcrossed with parent of dominant phenotype, no recessive individuals are obtained in the progeny. But when F₁is back crossed with its recessive parent, both phenotypes, dominant and recessive appeared in the progeny with ratio of 1:1.
• Monohybrid test cross gives a 1:1 phenotypic ratio.
• Dihybrid test cross gives a 1:1:1:1 phenotypic ratio,indicating that two pairs of factors are segregating and assorting independently.