CBSE Class 10 Answered

Mendel carried out a series of crossing experiments using pea plants. First series of experiments were carried out with a single pair of contrasting characters such as height or colour or shape etc. He selected 2 varieties of pea plants, say one with a tall stem and other with a dwarf stem. He then crossed these 2 plants. When the seeds were obtained and sown, the offsprings were all tall. This constituted the F1 generation. These hybrid talls of Fi generation were then self crossed. These gave rise to tall and dwarf offsprings in the ration 3:1. This constituted the F2 geneartion. This type of crossing in which only one pair of contrasting characters are considered is called a monohybrid cross.

In the crossing of a pure tall pea plant with a pure dwarf variety, the experiment can be shown as follows:

Pure tall      x      Pure dwarf

TT                             tt ........................... Parents

T                               t  ............................ Gametes

             Tt ................................................ Fi

   (Hybrid tall)

Tt       x     Tt ........................................... Selfing.