Let us denote the recessive gene for hairlessness with 'h' and the normal gene with 'H'. The rat terrier with hair can then have two possible genotypes, the homozygous HH and the heterozygous Hh. When we mate our rat terrier with another rat terrier that is hairless (homozygous recessive hh genotype), we can assess the genotype of our dog. The punnett squares in the images show the possible genotype of our dog.
