If the phenotypic ration is 3:1 then the underlying genotypic ratio will be 1:2:1.
The genotype of an individual is their own DNA pattern. More specifically, the two alleles a person acquired for a particular gene are referred to by this phrase. The observable character of this genotype is called a phenotype.
The genotype of an organism is the particular arrangement of alleles for a particular gene.
As an illustration, the genotypes for the flower-color gene in the pea plants were red-red, red-white, and white-white. The physical representation of an organism's allelic combination is called a phenotype.
for example let us take the example of the height of pea plant. the T represent tall plant (dominant) while t represents short/dwarf plant (recessive).
In this monohybrid cross the phenotypic ratio observed is 3:1 i.e., three tall plants and one dwarf plant.
However the genotypes of the four offspring will be TT, Tt, Tt, tt.