If members of the F1 generation are allowed to self-pollinate, the genetic ratio in the F2 generation will be 1:2:1 (homozygous dominant: heterozygous: homozygous recessive) for a monohybrid cross, meaning a single gene trait is being studied. 

Explanation:

• F1 generation:

  When two homozygous parents with contrasting traits are crossed, the F1 generation will all be heterozygous, exhibiting the dominant phenotype. 

• Self-pollination of F1:

  When these F1 heterozygotes self-pollinate, the offspring in the F2 generation will segregate the alleles according to Mendel's law of segregation, resulting in a 1:2:1 genotypic ratio. 

• The genetic ratio of the F2 shows that there will be 3 tall and 1 short offspring plants.(See diagram above)