In a cross of purple flowered heterozygous plants (Pp), the letter P represents the allele for purple flowers and the letter p represents the allele for white flowers. What is the probability that an offspring of this cross expresses plants with purple flower phenotypes? A. 0 B. 1/4 C. 1/2 D. 3/4

D (3/4)

Explanation:

This cross involves a single gene coding for flower colour in pea plant where the purple allele (P) is dominant over the white allele (p) since the purple allele masks the expression of the white allele in a heterozygous state (Pp). A cross between two heterozygous plants (Pp) will produce four possible offsprings with genotypes PP, Pp and pp in the ratio 1:2:1.

The PP and Pp genotypes are purple flowered while the pp is white flowered. Hence, the probability of having purple flowered plants from this cross is 3 out of 4 i.e. 3/4.