Biology Regents Practice Exam

Which factor most directly affects the expression of genetic traits in an individual organism?

1. The organism's DNA sequence.

2. The genetic makeup of its parents.

3. The environment in which it develops.

4. Its age at maturity.

The correct answer is: The environment in which it develops.

The factor that most directly affects the expression of genetic traits in an individual organism is the organism's DNA sequence. The DNA sequence contains the specific instructions for making proteins and other molecules that determine an organism's traits. These traits can include characteristics such as eye color, height, and susceptibility to certain diseases. While the genetic makeup of the parents provides the hereditary information, it is ultimately the specific arrangement of nucleotides in an individual’s DNA that dictates how those traits will manifest. This means that even if two individuals share the same genetic lineage, variations in their DNA can lead to different expressions of traits. The environment also plays a crucial role in how genetic traits are expressed. Factors such as nutrition, temperature, and exposure to chemicals can influence gene expression. For instance, some genes may only be activated in response to specific environmental conditions, showcasing the interaction between an organism’s genetic information and its surroundings. Age at maturity can impact the expression of traits over time, as certain traits may become more pronounced or developed as an organism ages. However, it is fundamentally the DNA sequence that holds the primary instructions that ultimately affect how traits are expressed, regardless of external influences or developmental stages.