Question

tt mates with Tt. What will be characteristic of offspring
A. 75% recessive
B. 50% recessive
C. 25% recessive
D. All dominant

Answer 1

Mendel gave the laws of inheritance of 7 traits in the pea plant. Each of the traits had 2 forms i.e. dominant and recessive. The form which expresses itself the most is known as the dominant while the latter is the opposite of the former. The experiment of self-pollination resulted in the occurrence of one trait in all generations while the experiment of cross-breeding showed different results in the first and second generation. The progeny of the first generation only possessed dominant traits while the second generation possessed recessive traits too.

Complete answer:

| T | t
---|---|---
t | Tt| Tt
t | Tt| tt

As you can see the above table shared, the progeny is showing both the traits so the two offsprings will be tall and two will be short i.e. The ratio will be 1:1 in phenotype and genotype.
Option A- 75% recessive
There are fewer chances of the progeny showing 75% recessive traits while 75% of dominant traits are possible in second-generation after cross-breeding.
Option B- 50% recessive
The ratio of 1:1 when calculated gives 50% of dominant tall and 50% of recessive short plants.
Option C- 25% recessive
25% of recessive traits are shown in the second generation on cross-breeding.
Option D- All dominant
This is possible in first-generation when the plants are self-pollinated, showing dominant traits.

Thus, the correct option is option B- 50% recessive.

Note: The seven important traits of the pea plants are seed shape- round or wrinkled, seed colour- yellow or green, flower colour- purple or white, flower position- axial or terminal, plant height- tall or short, pod shape- inflated or constricted and pod colour- green or yellow (Former being the dominant trait while the latter is the recessive one). The ${F_1}$ generation shows only dominant traits while the ${F_2}$ generation shows 3:1 phenotypic ratio that means 3 purple flowers and 1 white and 1:2:1 genotype ratio.