$F_2$ generation in a Mendelian cross showed that both genotypic and phenotypic ratios are same as $1:2:1$. It represents a case of:

In incomplete dominance (e.g., flower colour in Mirabilis jalapa), the heterozygote has a phenotype intermediate between the two homozygotes.Cross: $RR$ (Red) $\times$ $rr$ (White) $\to$ $Rr$ (Pink).$F_2$ results: 1 Red ($RR$) : 2 Pink ($Rr$) : 1 White ($rr$).Both the genotypic ratio and the phenotypic ratio are $1:2:1$.