Final answer:
The 'passive' effect of a genotype is seen when environmental factors play a role in the expression of traits, which is option C. This occurs independently of whether alleles are dominant or recessive, as the environment can influence the expression of the genotype, leading to variations in the phenotype.
Step-by-step explanation:
The question 'A "passive" effect of a genotype is seen when?' refers to the situation in which a genotype's impact is not due to its own active expression, but rather to the influence of the environment or different dynamics within the organism. Therefore, the correct answer is C. Environmental factors play a role.
When we discuss dominant and recessive alleles, we're referring to how certain traits are expressed in an organism. Dominant alleles are those that will express their traits in both homozygous (AA) and heterozygous (Aa) forms. On the other hand, recessive alleles only express their traits when two copies are present (aa), meaning they are both homozygous and recessive. Despite the presence of a recessive allele, if a dominant allele exists, it will mask the recessive trait. This concept is in line with Mendel's principles of inheritance, where the dominant allele is the expressed unit factor, whereas the recessive allele is considered the latent unit factor.
However, environmental factors can also influence the expression of the genotype in an organism. This means that the genotype's potential can be moderated or completely altered by the environment, leading to what can be considered as a 'passive' effect on the phenotype.