Final answer:
The allele for sandy-colored fur was likely dominant as observed by the 3:1 phenotypic ratio in the cubs, which correlates with expected outcomes of a monohybrid cross involving dominant and recessive alleles.
Step-by-step explanation:
If three out of four cubs from the cross had sandy-colored fur, the allele for sandy-colored fur was most likely dominant. This deduction comes from the fact that the dominant allele tends to visibly affect the phenotype of the organism when present, which means that it only takes one copy of the dominant allele to display the trait, as opposed to needing two copies for a recessive trait to be expressed. Also, referencing Mendelian genetics, when a monohybrid cross is conducted, and the traits follow a dominant and recessive pattern, we usually expect to see a phenotypic ratio of 3:1 in the offspring, meaning three with the dominant phenotype for every one with the recessive phenotype.
This ratio aligns with the scenario described, where three-fourths of the offspring—you can think of this as the 3 in the 3:1 ratio—exhibit sandy-colored fur, presumably the dominant phenotype. The Punnett square often used to predict the outcome of monohybrid crosses would show that if both parents were heterozygous for fur color, you would see this ratio. It does not necessarily mean that the allele is heterozygous in itself since 'heterozygous' refers to the genotype of an individual organism, not to the allele.