In Antirrhinum majus (snapdragon), a plant pure-breeding for tall stems and red flowers is crossed with a plant pure-breeding for dwarf stems and white flowers. All the F₁ plants are found to be tall with pink flowers. If these F₁ plants are self-pollinated, what is the expected proportion of dwarf plants with pink flowers in the F₂ generation? (Assume independent assortment of the two characters)

Step-by-step solution

Let the gene for stem height be T/t and for flower colour be R/r . The F₁ plants are tall, indicating that tallness ( T ) is completely dominant over dwarfness ( t ). The F₁ plants have pink flowers, indicating incomplete dominance between red ( R ) and white ( r ) flower colours. The genotype of the F₁ plants is TtRr . When F₁ plants are self-pollinated ( TtRr TtRr ): For stem height, the cross Tt Tt yields 3 4 tall and 1 4 dwarf plants. For flower colour, the cross Rr Rr yields 1 4 red, 1 2 pink, and 1 4 white fl