Mendel used Pea plant for his experiment.

Why Mendel choose pea plant only?

→ Short life span.

→ Production of large number of seeds.

→ Availability of seven different contracting characters. (for study)

Mendel was KNOWN as the father of genetics. He worked with and crossed the two pea plants with one and two pairs of contrasting characters.

Cross between two pea plants having one pair of contrasting CHARACTER is known as Monohybird cross. On the other hand cross between two pea plants having two pairs of contrasting characters is known as Dihybrid cross.

In Monohybrid cross; he made a cross between a plant having Tall (TT) characters and another pea plant having short (tt) characters. Plant having characteristics of tall is Dominant trait and another having short characters is Recessive trait.

In the first generation or in F1 generation all progeny SHOWS Tall (Tt) plant while in the second progeny or in F2 generation; the cross was between TT and Tt. Here that,

In the first generation or in F1 generation all progeny shows Tall (Tt) plant while in the second progeny or in F2 generation; the cross was between TT and Tt. Here that,Genotypic ratio is 1:2:1 (TT:Tt:tt) and Phenotypic ratio is 3:1 (Tall:Short)

In Dihybrid cross; he made a cross between a plant having ROUND yellow seeds and another pea plant having wrinkled seeds. Round yellow seeds were denoted by RRYY and wrinkled seeds were denoted by rryy. Both pea plants were homozygous in nature (RRYY and rryy).

In the first generation all progeny shows round yellow seeds (RrYy). Because round and yellow seeds both were dominant characters (which can express themselves in next generation) whereas green and wrinkled seeds are recessive character (which can't express themselves in next generation).

Whereas in the second generation; the Phenotypic ratio is 9:3:3:1 (Round Yellow:Round Green: Wrinkled Yellow: Wrinkled Green)

[ Refer the attachment for Monohybrid and Dihybrid cross ]