First generation after a cross is

Definitions / Explanation : Genotype
 

Mendel crossed a pure white-flowered recessive pea plant with a dominant pure red-flowered plant. The first generation of hybrids from the cross should show

In a monohybrid cross of plants with red and white flowered plants, Mendel got only red flowered plants. On self-pollinating these $F_1$ plants got both red and white flowered plants in $3:1$ ratio. Explain the basis of using $RR$ and $rr$  symbols to represent the geno type of plants of parental generation.

The law of segregation of characters is also called the law of purity of gametes because