Final answer:
In classical Mendelian inheritance, a characteristic would typically exhibit a 3:1 phenotypic ratio for offspring, representing the dominance of one allele over the recessive allele. Variations exist, such as a 2:1 ratio in the presence of a lethal allele that affects the genotypic ratio of observed offspring.
Step-by-step explanation:
If a characteristic exhibits classical Mendelian inheritance, then based on the information provided and understanding Mendel's principles, a 3:1 ratio of phenotypes would be produced in the offspring. This is seen in the case of Mendel's monohybrid cross where one gene has two alleles, and the dominant allele hides the presence of the recessive allele in the phenotype. For example, if the parents are both heterozygous for a trait (Aa) and follow Mendelian inheritance patterns, the possible genotypes of their offspring in a Punnett square would be AA, Aa, Aa, and aa, which translates to a 3:1 ratio of dominant to recessive phenotypes.
When dealing with lethal alleles or more complex genetic interactions like two-gene interactions, the expected ratios can change. In the case of a mating between two heterozygous individuals for a recessive lethal allele expressed in utero, the genotypic ratio would be 2:1 (heterozygous:homozygous dominant) because the homozygous recessive genotype leads to death before birth and is not present in the observed offspring.
The question also refers to two-gene interactions, often considered in dihybrid crosses, where a 9:3:3:1 phenotypic ratio is typical, assuming the genes assort independently and are not linked. This corresponds to the classic Mendelian inheritance of two traits governed by two different gene pairs.