Question

a pea plant with genotype pp (purple flowers) mates with a plant with the genotype pp (white flowers). the dominant allele p codes for purple flowers. the possibility that the offspring will have purple flowers is 50% if an offspring from this cross mates with a pp, the possibility of homozygous dominant genotype for the flowers will be 0%

Explanation:

Step1: Analyze the cross between PP and pp

When a pea plant with genotype PP (purple flowers) mates with a plant with genotype pp (white flowers), all the offspring will have the genotype Pp. Since the dominant allele P codes for purple flowers, all these offspring (100%) will have purple flowers.

Step2: Analyze the cross between Pp (from the first - generation) and pp

When an offspring (Pp) from the first cross mates with a pp plant. The possible gametes from Pp are P and p, and from pp are p and p. Using a Punnett square:

	p	p
p	pp	pp

The genotypes of the offspring are Pp (purple) and pp (white) in a 1:1 ratio. So the probability of having purple flowers (Pp) is 50%.

Answer:

The homozygous dominant genotype for the flowers will be 100%. The possibility that the offspring will have purple flowers is 50%.