In a classic Mendelian monohybrid cross, the ratio of dominant to recessive phenotypes in the F2 generation is 3:1.

Here's why:

* F1 generation: When two homozygous parents (one dominant, one recessive) are crossed, all offspring in the F1 generation will be heterozygous, exhibiting the dominant phenotype.

* F2 generation: When two F1 individuals are crossed, the following combinations of alleles are possible in their offspring:

* 1/4 chance of getting the dominant homozygous genotype (AA)

* 1/2 chance of getting the heterozygous genotype (Aa)

* 1/4 chance of getting the recessive homozygous genotype (aa)

Since both AA and Aa genotypes express the dominant phenotype, the ratio of dominant to recessive phenotypes in the F2 generation becomes 3:1.