Biology · Principles of Inheritance and Variation · NEET
The garden pea (Pisum sativum) had a special mix of features that no random plant offered together. It showed many clear contrasting traits (tall/dwarf, round/wrinkled seeds), it self-pollinates naturally so it stays pure, its flower can still be opened for hand-crossing, it has a short life cycle, and it produces many seeds. This combination let Mendel run clean, countable experiments. For NEET, remember it was a deliberate choice, not luck.
A contrasting trait is a character that appears in two clearly different, easy-to-tell-apart forms with nothing in between, like flower colour violet or white. Mendel studied seven pairs of contrasting traits in pea: stem height, flower colour, flower position, pod shape, pod colour, seed shape, and seed colour. NEET loves asking which trait was NOT studied (trichomes is a common wrong option).
In pea, the anther and stigma sit inside a closed flower, so pollen usually falls on the same flower's stigma. This self-pollination, repeated over generations, gives true-breeding (pure line) plants that always produce offspring identical to themselves for a trait. Pure parents are essential, otherwise Mendel could not be sure what alleles the parents carried. So self-pollination = built-in pure lines.
Even though pea normally self-pollinates, its flower can be opened by hand. Mendel removed the anthers early (this is called emasculation) so the flower could not self-pollinate, then dusted pollen from a different plant onto the stigma. This artificial cross-pollination (hybridisation) let him make crosses between two chosen parents. So pea gives BOTH self-pollination for pure lines AND easy hand-crossing.
Mendel used statistics and maths for the first time in biology, so he needed large numbers to see clear ratios like 3:1. A pea plant gives many seeds per plant, so he could count hundreds of offspring. A short life cycle meant he could grow several generations (P, F1, F2, F3) in a few years. He did his experiments over seven years, from 1856 to 1863.
Mendel selected 14 true-breeding pea varieties, arranged as 7 pairs. Each pair was similar except for one character that came in two contrasting forms (for example, one pure tall and one pure dwarf line). These 14 varieties gave him the 7 pairs of contrasting traits he studied. The number 14 is a direct NEET fact (NEET 2020 asked it).
Among the following characters, which one was not considered by Mendel in his experiments on pea?
How many true breeding pea plant varieties did Mendel select as pairs, which were similar except in one character with contrasting traits?
Which one from those given below is the period for Mendel's hybridization experiments?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Pisum sativum. It is a self-pollinating legume with clear contrasting traits, which is why Mendel picked it.
In effect, yes. Repeated self-pollination keeps the plant pure for a trait, producing true-breeding (pure line) plants that Mendel needed as parents.
Yes. He removed the anthers (emasculation) to stop self-pollination, then hand-transferred pollen from a chosen plant. This artificial cross-pollination let him make specific crosses.
NEET often tests the seven characters and asks which one was NOT studied. Knowing the exact seven lets you reject fake options like trichome type instantly.
Large seed numbers let him see clear ratios (like 3:1). Applying statistics to biology for the first time made his laws reliable, not just guesses.
