a plant can produce either purple flowers or white flower. What is the probability of purple-flowered offspring if two plants are heterozygous for purple flowers are crossed?

Let us consider a cross between two plants heterozygous for purple flowers.

Heterozygous Purple (Pp) X Heterozygous Purple (Pp)

Each plant will produce two types of gametes, i. e. 50% gametes carrying (P) allele and 50 % carrying (p) allele.

Checking the probability of fusion between the gametes produced by two plants crossed using Punnet Square method, it is seen that 75% plants will have at least one dominant allele (P) and thus will bear purple flowers. Only 25% plants will have recessive allele in homozygous state (pp). These plants will bear white flowers.

Out of 75% plants bearing purple flowers, 25% will be homozygous Purple (PP) and 50% will be heterozygous purple (Pp)