What is a key characteristic of Parkinson's disease?

A key characteristic of Parkinson's disease is the gradual loss of muscle coordination and balance. This neurodegenerative disorder primarily impacts motor function due to the degeneration of dopamine-producing neurons in a specific area of the brain known as the substantia nigra. As these neurons deteriorate, the brain's ability to coordinate movement is compromised, leading to symptoms such as tremors, stiffness, and bradykinesia (slowness of movement). Over time, individuals may experience difficulty with balance and a general decline in physical abilities, emphasizing the progressive nature of the condition.

This characteristic stands out, especially considering the other options. While there are genetic factors involved in some cases of Parkinson's, the disease is not solely the result of a dominant allele. Furthermore, Parkinson's involves a decrease in dopamine, not an increase, leading to the hallmark symptoms of the condition. Lastly, although it commonly affects older adults, it can begin earlier in life, demonstrating that age is not the sole determinant in its onset. Hence, the emphasis on gradual loss of coordination and balance captures the essence of the disorder.