Question

how did Mendel explain that it ts possible that a trait is inherited but not expressed in an organism

Answer 1

He called it a recessive gene and that they are not shown unless you have two recessive gene like rr not Rr

Answer 2

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Mendel crossed a tall pea plant and a short pea plant of different characteristics and are produced progeny from them. The first generation (F₁) plants were all of them were tall. However, when the F₁ generation plants were crossed, the second (F₂) generation plants were not all of them were tall. Only, one-quarter of them was short. This indicates that both the tall and short traits were inherited in the F₁ plants but only the tallness trait was expressed.

This shows that it is possible that a trait is inherited but not expressed in an organism.