Question

When a true breeding tall plant containing red flowers was crossed with the true breeding dwarf plant containing white flowers, all F1 plants were tall with red flowers. When the F1 plant was self-pollinated, considering independent assortment of plant height and flower colour traits, the calculated percentage probability of dwarf plants bearing red flowers in the F2 generation is ________ percent (round off to 2 decimal places).

Hint:

To find the probability of two independent events occurring together, multiply the probabilities of each event.

Answer 1

Correct Answer: 18.75

In this genetic cross, we are dealing with two traits: plant height (T for tall and t for dwarf) and flower colour (R for red and r for white).
- The F1 generation is heterozygous for both traits (TtRr), as it is the result of crossing two true-breeding parents.
- The self-pollination of the F1 generation will give rise to a Punnett square for both traits, which follows the Mendelian inheritance pattern.
For the height trait, the ratio in the F2 generation will be: \[ Tt \times Tt \quad \Rightarrow \quad 1 \, \text{T:} \, 2 \, \text{Tt:} \, 1 \, \text{tt} \quad \Rightarrow \quad \text{3 tall : 1 dwarf}. \] For the flower colour trait, the ratio will be: \[ Rr \times Rr \quad \Rightarrow \quad 1 \, \text{RR:} \, 2 \, \text{Rr:} \, 1 \, \text{rr} \quad \Rightarrow \quad \text{3 red : 1 white}. \] We are interested in the probability of dwarf plants with red flowers. The probability of a dwarf plant is \( \frac{1}{4} \) (from the height trait) and the probability of red flowers is \( \frac{3}{4} \) (from the flower colour trait). Therefore, the probability of both occurring together is: \[ P(\text{dwarf and red}) = \frac{1}{4} \times \frac{3}{4} = \frac{3}{16}. \] Thus, the calculated percentage probability is: \[ \frac{3}{16} \times 100 = 18.75 %. \] Therefore, the percentage probability of dwarf plants bearing red flowers in the F2 generation is \( \boxed{18.75} \).