Question

what is a test cross? how does it differ from a back cross..

Answer 1

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...
In test cross, F1 hybrid is crossed back with the recessive parent. In other words, test cross is the cross between a dominant phenotype (TT or Tt) and a homozygous recessive (tt). Mendel was the first person to perform the test cross to identify whether an individual is heterozygous or homozygous for dominant character. Other than discovering heterozygosity, test cross is also useful to check the purity of the gametes produced by parents.

If homozygous dominant F1 hybrid (TT) is crossed with the recessive parent, it will always result receive 100% heterozygous tall hybrids.



If heterozygous dominant F1 hybrid (Tt) is test crossed with the recessive parent, only 50% will be tall and the rest 50% will be dwarf.

Answer 2

test cross is crossing that offspring or hybrid to a homozygous recessive parent only...it is used to determine whether the offspring is homozygous dominant or heterozygous dominant.
back cross is crossing the offspring wid any one of its parents