Answer:
A cross between a homozygous purple flower (PP) and homozygous white flower (pp)
Explanation:
This cross involves a single gene coding for flower colour in pea plants. One allele is responsible for purple color (P) is dominant over another allele responsible for white colour (p) i.e. P allele will mask the expression of p allele.
According to the question, a cross between a purple-flowered plant and a white-flowered plant produced an all purple-flowered offsprings. This implies that both parents were homozygous for the two traits i.e. they contained identical alleles for the flower colour gene.
The purple color plant has a genotype: PP while the white color plant has a genotype: pp, to produce F1 offsprings will genotype Pp. All 73 offsprings produced in this cross and heterozygous i.e. a combination of purple and white alleles.
