Dr. Orr is the Tulloch professor of genetics in the department, directs the Institute of Translational Neuroscience, and is a member of the Division of Molecular Pathology and Genomics. His research is focused on the molecular genetics of neurodegenerative diseases, principally the autosomal dominant form of spinocerebellar ataxia (SCA1). Patients usually develop SCA1 in mid-life. They experience loss of motor coordination and develop slurred speech, spasticity, and cognitive impairment. These symptoms arise from the loss of Purkinje cells and damage to other nerve cells in the brain’s cerebellar cortex. Orr and his colleagues cloned the SCA1 gene and found that the disease is caused by the expansion of an unstable, repeated cytosine-adenine-guanine (CAG) sequence in DNA. The length of the trinucleotide repeat is associated with when symptoms develop.