Final answer:
The deletion of the HoxB-1 gene could severely impact hindbrain development and the function of facial motor nerves, potentially causing difficulties in facial expressions or swallowing due to improper growth or patterning of the associated nerves.
Step-by-step explanation:
The deletion of the HoxB-1 gene could have profound consequences for nervous system development, especially in the formation of rhombomeres and the function of the facial motor nerve. Hox genes, which include HoxB-1, encode transcription factors that are pivotal in the embryonic development of animals, dictating the body plan and segment identity. Rhombomeres are segments in the developing hindbrain that give rise to nerves controlling facial expressions among other functions. The removal of the HoxB-1 gene could lead to mis-specification of rhombomere-derived neurons and potentially to improper growth or patterning of the associated facial motor nerve, ultimately impacting facial movements or expressions.
Looking at the impact of Hox gene mutations in organisms like fruit flies, where a single mutation can cause legs to grow where antennae should be, an analogous mutation in vertebrates, such as a deletion of HoxB-1, can cause neurological defects due to incorrect regional identity in the brain. Without HoxB-1, specific regions in the hindbrain might not develop properly, leading to consequences such as loss of function in cranial nerves, with potential deficits in sensory and motor control, especially in the face. Problems in facial motor nerve functions might manifest as difficulty in facial expressions or swallowing, due to the disruption in the normal development of neural circuits responsible for these actions.