Explain what is a test cross and a back cross as done by GJ Mendel?Also, What will the genotypic and phenotypic ratios of both of these crosses(Dihybrid) ?

Difference between Test Cross and Backcross
• All test crosses are considered as backcrosses, but all backcrosses are not the test crosses.
• During backcross, F1 hybrid is crossed back with any of the parents, eit her homozygous or heterozygous. However, during test cross, F 1 hybrid is always crossed back with the recessive parent.

Test cross : You know that a person showing a dominant trait can have genotype as homozygous or heterozygous. So this cross is done to detemine if the organism with dominant phenotype is heterozygous or homozygous dominant.

All you have to do is to breed this particular organsim having recessive phenotype.By seeing the phenotype of offsprings you can easily know the genotype of the parent which was showing dominant trait. please see the attached picture for more information. As you can see themonohybrid test cross of heterozygous dominant with pure recessive gives a 1: 1 phenotypic ratio.


Test cross of dihybrid is as follows