In pea plants, tall (T) plants are dominant over short (t) plants. If a heterozygous (Tt) pea plant is crossed with a homozygous dominant (TT) pea plant, all of the resulting pea plants should be tall (TT or Tt). Each plant will receive a dominant allele from the homozygous dominant plant, while they could receive either a dominant or recessive allele from the heterozygous plant.

The fact that each plant gets only one allele from each parent plant is detailed in the law of _______.

Law of segregation states that the two factors for a trait, present together in an individual, do not get mixed and are separated during gamete formation. It is also called as principle of purity as the segregation of two factors is responsible for purity of gametes. So, a plant with genotype "TT" forms all gametes having only one copy of allele "T" while the parent plant with genotype "tt" forms all the gametes having one copy of allele "t". Hence, each plant gets only one allele from each parent plant.