Final answer:
Quantitative variation in a trait can be influenced by six simple Mendelian loci, each having two alleles.
Step-by-step explanation:
Quantitative variation in a trait can be caused by as few as six simple Mendelian loci that each have two alleles. This corresponds to option B. When considering genetics and traits, it is also important to remember that Mendel's initial hypothesis stated that there could only be two alleles for a given gene, one being dominant and the other recessive. We now understand, however, that this was an oversimplification. In fact, multiple alleles may exist within a population, providing a variety of combinations at the genetic level.
For example, the ABO blood type system in humans includes three alleles, showcasing that more than two alleles for a particular gene can be present in a population. This concept is critical in the field of population genetics, which explores how alleles among a population are inherited and how they evolve over time.
Moreover, when working through genetics problems, one should recognize that any characteristic showing a total phenotypic ratio of 16 likely suggests a two-gene interaction.