How did Mendel experiments show that traits may be dominant or recessive? (Pls do not show cross just tell the writing part in details)

Dear Student,

A dominant allele is defined as the allele which masks the expression of recessive allele and expresses itself, when present in heterozygous condition. The phenotypic effect of the dominant allele is known as the dominant trait. while the phenotypic effect of the recessive allele is known as the recessive trait.  

During Mendel's experiment true breeding or homozygous plants showing the different forms of a trait were crossed. 

For example: Plant height was the chosen trait. There existed two forms for plant height; Tall and short. So, Mendel selected plants which always produced plants with tall height and plants which always produced plants with tall height. On crossing such plants he found that all the offsprings were tall. 

Parents: TT x tt

Gametes: T , t

F1 generation: Tt

All the plants of the F1 generation will be heterozygous tall (Tt). So, this indicated that tall plant height is the dominant trait. 

Next he self fertilized these tall plants, and he found out that a few of the offsprings were of short height while the major portion was tall. 

F2 generation: Tt x Tt

So, the phenotypic ratio of the given cross is tall:short :: 3:1. Out of the four plants three will be tall and one will be short. Therefore, short height was the recessive trait.

Regards