Question

Assume that blue flowered plant is dominant character over the white. When a blue flowered plant is crossed with its white flowered plant, the progeny showed 50% of plants with blue flowers is with white flowers. The genotypes of blue and white parents respectively are

• A. bb, bb
• B. BB, Bb
• C. BB, bb
• D. Bb, bb

Answer 1

Answer: (D)

Bb, bb

According to the question, the blue flower color is dominant over white flowers. Option A is incorrect as the blue flowering plants will have atleast one copy of dominant allele “B” to exhibit the “blue flower” phenotype.
Option B is incorrect as the presence of a single copy of dominant allele “B” would mask the expression of recessive allele ‘b”; hence the white flowering plants in parent generation will have two copies of recessive allele “b” which makes its genotype “bb”. A homozygous dominant (BB) and homozygous recessive parent (bb) plants would produce all blue flowered progeny. Therefore, the genotype of dominant parent would be “Bb”. This makes option D the correct answer.