A hypothetical flowering plant produces blue, light blue, and white flowers. To determine the inheritance pattern, the following crosses were conducted with the results indicated:

blue x blue * all blue

white x white all white

blue x white * all light blue

What type of inheritance pattern does this represent?

a. simple Mendelian

b. X-Iinked

c. codominance

d. incomplete dominance

e. pleiotropy

d. incomplete dominance

Explanation:

When none of the alleles of a particular locus completely masks the expression of the other allele of the same gene, it is called incomplete dominance. If the allele B gives "blue" phenotype and allele b gives white phenotype, a cross between blue (BB) and white (bb) parents would produce all the progeny with genotype Bb. Since the allele B does not completely prevent the expression of allele b in the heterozygous condition, the phenotype of the F1 hybrids would be "light blue". Therefore, it is an example of incomplete dominance.

blue (BB) x blue (BB) = all blue (BB)

white (bb) x white (bb) = all white (bb)

blue (BB) x white (bb) = all light blue (Bb)