Cross a heterozygous individual with a homozygous recessive one determine the genotype ratio and phenotype ratio of their offspring

Let's have our alleles be J = dominant, j = recessive. And for fun let's make the dominant phenotype black coat, the recessive brown coat.

Heterozygous x homozygous recessive

   = Jj x jj

Punnett square:

       J        j

j      Jj        jj

j      Jj        jj

Genotypic ratio: 2 Jj : 2 jj, or a one-to-one ratio of Jj to jj.

Phenotypic ratio: 2 black : 2 brown, or a one-to-one ratio of black to brown.