Question

When a pure-tall pea plant is crossed with a pure-dwarf pea plant, the percentage of tall pea plants in F1 and F2 generation pea plants will be respectively:

• A. 100%; 25%
• B. 100%; 50%
• C. 100%; 75%
• D. 100%; 100%

Hint:

In a simple Mendelian cross, dominant traits like tall (T) mask the recessive dwarf trait (t). The F1 generation is all heterozygous (Tt), and the F2 generation follows a 3:1 ratio.

Answer 1

The Correct Option is A

This question refers to a Mendelian monohybrid cross between a pure tall pea plant (TT) and a pure dwarf pea plant (tt). The F1 generation will be a cross between these two, resulting in all tall plants (Tt), as the tall allele is dominant over the dwarf allele. For the F2 generation, we cross two F1 plants (Tt x Tt): \[ \text{Gametes from } Tt \rightarrow T, t \] The Punnett square will give the following genotypes: \[ \begin{array}{c|cc} & T & t \\ \hline T & TT & Tt \\ t & Tt & tt \\ \end{array} \] From this, we can see the genotype ratio for F2 generation is: \[ \text{Tall (TT or Tt)} : \text{Dwarf (tt)} = 3 : 1 \] Thus, 75% will be tall and 25% will be dwarf. Hence, the correct answer is option (1).