Humber Admissions Practice Test 2026 - Free Practice Questions and Study Guide for Humber College Admissions

The correct answer highlights the significant role that environmental factors play in influencing traits by interacting with alleles. Environmental influences, such as temperature, nutrition, and exposure to toxins or pathogens, can affect how genes are expressed, leading to variations in traits within a population.

For instance, the phenotype of an organism, which is its observable characteristics, can change in response to environmental conditions. A classic example is the color of hydrangea flowers, which can change based on the pH of the soil, despite having the same genetic potential. This showcases how the environment can modify trait expression, demonstrating that alleles do not operate in isolation but rather in conjunction with external conditions.

The other choices suggest that environmental influence is nonexistent, that traits are solely determined by genetics without any interaction, or that only dominant alleles are impacted, which overlooks the complexity of genetic expression and the importance of both genetics and environment in shaping phenotypic variation.