Which motor disorder is marked by loss of coordination?

The choice of ataxia as the correct answer is appropriate because ataxia specifically refers to a neurological disorder that impairs coordination and balance. It results from dysfunction in the cerebellum or the pathways that connect the brain to other parts of the central nervous system, leading to difficulties in controlling movements. Individuals with ataxia may exhibit unsteady movements, trouble with fine motor tasks, and overall clumsiness due to this loss of coordination.

In contrast, while Parkinson's disease is characterized by tremors, stiffness, and bradykinesia, it primarily affects the control of movement but does not specifically denote a loss of coordination in the same way. Huntington's disease, on the other hand, involves uncontrolled movements and cognitive decline but is not primarily defined by coordination issues. Dystonia involves abnormal muscle contractions and posturing rather than a generalized loss of coordination. Therefore, ataxia stands out as the motor disorder distinctly marked by loss of coordination, making it the most accurate answer.