Answer:
Genotypic ratio = 100% XxYyZz
Phenotypic ratio = 100% tall, fat, fair.
Explanation:
For a trihybrid cross involving the genes XX which codes for tallness, YY which codes for fatness, and ZZ which codes for fairness with their alternate forms being xx, yy, and zz respectively; each gene will segregate into their respective alleles and combine to form gametes during meiosis, such that:
XXYYZZ ----> XYZ, XYZ, XYZ, XYZ, XYZ, XYZ, XYZ, XYZ
xxyyzz -----> xyz, xyz, xyz, xyz, xyz, xyz, xyz, xyz
These gametes then combine randomly during fertilization to give all XxYyZz offspring.
XYZ x xyz
XxYyZz
Since X is dominant over x, Y is dominant over y, and Z is dominant over z, then XxYyZz individuals that are produced from the cross would be tall, fat, and fair. Hence
Genotypic ratio = 100% XxYyZz
Phenotypic ratio = 100% tall, fat, fair.
See the attached image from the Punnet's square analysis.
