Question

Define monohybrid cross.

Answer 1

Monohybrid cross: A cross that involves two parents that differ in only one trait is called a monohybrid cross.

1. In a monohybrid cross, we will study the inheritance of one pair of contrasting characteristics ‘tallness’ and ‘dwarfness’ of the pea plants by their first-generation and second-generation progeny.
2. For example, the inheritance of tall and dwarf characters is said to be a monohybrid cross.
3. Mendel first crossed pure-bred tall pea plants with pure-bred dwarf pea plants and found that only tall pea plants were produced in the F₁ generation
4. No dwarf pea plants or short pea plants were obtained in the first generation of progeny.
5. Mendel concluded that the first generation (or $F_1$ cross) showed the traits of only one of the parent plants: tallness.
6. The trait of the other parent plants, dwarfness, did not show up in the progeny of the first generation.
7. Mendel then crossed the tall pea plants of the first generation ($F_1$ generation) and found that tall plants and dwarf plants were obtained in the second generation (or $F_2$ generation) in the ratio of $3:1$
8. In the $F_2$ generation, three-fourths of plants were tall, and one-fourth were dwarfs.
9. Mendel noted that the dwarf trait of the parent pea plant, which had seemingly disappeared in the first generation progeny, reappeared in the second generation.