Final answer:
In degenerative spondylolisthesis, the traversing nerve root is the one generally affected due to the narrowing of the spinal canal, while the exiting nerve root is less likely to be compressed.
Step-by-step explanation:
With degenerative spondylolisthesis, the nerve root that is typically affected is the traversing nerve root, rather than the exiting nerve root. Spondylolisthesis is a condition that occurs when one vertebral body slips with respect to the adjacent vertebral body causing radicular or mechanical symptoms or pain. It is graded based on the degree of slippage of one vertebral body on the adjacent vertebral body. As the vertebra slips over the one below, it can lead to narrowing of the spinal canal where the traversing nerve roots pass. The exiting nerve root, however, is less commonly compressed because spondylolisthesis primarily affects the central spinal canal where the traversing roots are located rather than the intervertebral foramen from which the exiting roots emerge.