Biology Regents Practice Exam

How can the external environment affect gene expression in organisms?

1. It determines the number of offspring produced

2. It influences the distribution of genes within a population

3. It can change the fur color of animals based on temperature

4. It alters the overall DNA sequence

The correct answer is: It can change the fur color of animals based on temperature

Gene expression is the process by which information from a gene is used to synthesize functional gene products, often proteins. The external environment can significantly influence this process. Option C highlights a specific example of how environmental factors, such as temperature, can lead to changes in gene expression, which may result in phenotypic changes such as the fur color of animals. In some species, the temperature can trigger certain genes to be more or less active. For instance, in Arctic foxes and some species of hares, the fur color changes with the seasons, being white in winter for camouflage in snow and brown or gray in summer to blend in with the earth. This change occurs because the expression of genes responsible for producing different pigments in the fur is influenced by temperature, demonstrating a clear link between the external environment and gene expression. The other options are less relevant to the relationship between the external environment and gene expression. While the number of offspring produced (first choice) could be influenced by environmental conditions, it does not directly reflect the mechanisms of gene expression itself. The distribution of genes within a population (second choice) pertains to population genetics rather than individual gene expression changes. Lastly, altering the overall DNA sequence (fourth choice) involves mutations or genetic alterations,