Question

Evidence: Scientists found that the runners who sprinted the fastest had the highest amount of ACTN3 protein molecules in their bodies.

Do you think that this evidence shows that the ACTN3 protein determines running ability? Explain your ideas using the words protein, trait, and feature in your response.

Answer 1

The evidence suggests a correlation between ACTN3 protein levels and running ability, but running as a trait or feature involves multiple genetic and environmental factors. ACTN3 may influence muscle characteristics, yet natural selection and complex interactions define traits like running speed over time.

Step-by-step explanation:

The evidence that scientists found—that the runners who sprinted the fastest had the highest amount of ACTN3 protein molecules—suggests there may be a correlation between ACTN3 protein levels and running ability. However, it is important to note that the presence of a protein alone does not determine a trait or feature; rather, it is the interaction of many genetic factors and environmental influences that typically defines an individual's capability. The protein could be involved in the development of muscle characteristics conducive to sprinting, hence affecting the trait of running speed. Moreover, the feature of a runner's success is likely to depend on both genetic predispositions, such as those influenced by ACTN3 and other genes, and non-genetic factors like training, diet, and motivation.

When discussing traits like running speed, we often consider the different muscle fiber types—fast-twitch and slow-twitch. For instance, professional marathon runners are likely to have a higher proportion of slow-twitch muscle fibers, which are adapted for endurance (Figure 15.5.5), while sprinters tend to have more fast-twitch fibers, contributing to explosive power and speed. This muscle composition can be influenced by both the individual's genetic makeup, including the presence of proteins like ACTN3, and their training regimen.

Natural selection can lead to adaptations like improved running speed, but it is a process that occurs over generations through the reproduction of individuals with favorable genetic traits (d). The success of sprinters may not be solely attributed to high levels of the ACTN3 protein but may also include numerous other factors ranging from genetic to environmental variables.