Three Mark Questions :
What is a test cross? How can it decipher the heterozygosity of a plant?
A test cross is a cross between F1 progeny and its homozygous recessive parent. This cross determines whether the dominant character is coming from the homozygous dominant genotype or heterozygous genotype (e.g. tallness coming from TT or Tt). When TT is crossed with tt, we obtain all Tt (tall) individuals in the F1 progeny, whereas when Tt is crossed with tt, we obtain Tt (tall) and tt (dwarf) individuals in the F2 progeny. Thus, a test cross can be used to determine the heterozygosity of the plant.