i. When the F1 hybrid is crossed back with any one of the parents, it is called a back cross. Cross of F1 hybrid with homozygous recessive parent is test cross.
ii. A back cross can be a test cross, but all test crosses need not be back crosses. A back cross with dominant parent is not a test cross
iii. Back cross can be a dominant or recessive back cross.
iv. In dominant back cross, F1 individual is crossed with dominant parent and all progeny shows dominant character.
v. F1 hybrid tall plant (Tt) is crossed with dominant parent (TT), progeny will be TT or Tt. Genotypically and phenotypically all offsprings would be tall.
vi. In recessive back cross, F1 individual is crossed with recessive parent (tt).
vii. If progeny is Tt or tt genotypically and 50 % tall and 50 % dwarf phenotypically, then one can infer that F1 generation is heterozygous, i.e Tt.
viii. If progeny is TT genotypically, i.e all tall phenotypically, then one can infer that F1 generation is homozygous, i.e. TT
All offsprings are tall.
Thus, in back cross with dominant parent, all the progeny obtained show dominant character.
Recessive back cross (Test cross):
50% offsprings are tall and 50% dwarf.
Thus, test cross produced progeny with both dominant and recessive characters in equal proportion.
