Answer:
If a gray rat heterozygote (Gg) and a black rat heterozygote (Bb) were to breed, the following phenotypic and genotypic ratios would result:
Step-by-step explanation
 
 Gg (Heterozygous gray rat) X Bb (Heterozygous black rat)
 B b
 G GB Gb
 g gB gb
therefore, In offsprings, 50 % rats will be gray and 50 % rats will be black. So, both the ratios (phenotypic and genotypic) would be 50:50