This is a case of incomplete dominance, In a cross between heterozygotes b1b2 the ratio will be 1:2:1.
When both alleles of a gene are only partially expressed at a locus, it is known as incomplete dominance.
This sort of gene interaction frequently produces an intermediate or distinct phenotype. Additionally called partial dominance.
Pink blossoms of the four o'clock flower (Mirabilis Jalapa) and physical traits in people, such as hair color, hand sizes, and height, are instances of incomplete dominance.
When the two alleles combine to create a third phenotype that differs from both of the parents, this is known as incomplete dominance.
The standard illustration is when a red flower and a white flower are combined.
the cross for two individuals with genotype b1b2 is as follows:
b1b2 X b1b2 (parent)
b1b1, b1b2, b1b2, b2b2 (offspring)
thus the ratio will be 1:2:1 (blue: light blue: white)
