Question

how did mendel experiment that it is possible that a traits is inherited but not expressed in an organim

Answer 1

Mendel took pea plants with different characteristics - a tall plant and a short plant. He then produced progeny out of them.

In the first generation or F1 all plants were tall and none were short. Here only one trait was seen.

Then Mendel checked if the F1 plants were exactly as same as the plants from parent generation. This he did by getting both the F1 and parent plants to reproduce by self pollination.

The progeny of the parental plants were all tall but the progeny of the F1 generation were not all tall. A quarter of them were short.

This proves that both the tallness and shortness trait was inherited in the F1 generation but only the tallness trait was expressed.

Thus two copies of traits are inherited in each sexual reproducing organism.