The phenotype of the heterozygous pea plant with violet flowers is Vv (V for dominant violet allele and v for recessive white allele). The phenotype of the homozygous pea plant with white flowers is vv. This is a monohybrid cross. When we create a Punnett square for this cross, we have :
V
v
v
Vv (violet)
vv (white)
v
Vv (violet)
vv (white)
The Punnett square shows us that in this cross, half of the progeny will be heterozygous (Vv) with violet flowers (dominant trait), and the other half will be homozygous recessive (vv) with white flowers. Therefore, out of 40 progeny, we expect 20to have violet flowers and 20 to have white flowers.