Final answer:
The correct answer to the student's question is option a) The amelogenin gene, as it is responsible for the formation of tooth enamel, and a mutation could impede enamel and dentin production.
Step-by-step explanation:
The production of enamel and dentin in birds is related to specific genes responsible for these tissues. Enamel is the hard, protective outer covering of the dentin of the crown of a tooth. It is primarily composed of hydroxyapatite crystals and is produced by specific cells known as ameloblasts, which express the gene responsible for enamel formation. The most likely gene to be responsible for shutting off the enamel and dentin production with a single mutation would be a) The amelogenin gene. Amelogenin is a critical protein in the formation of enamel. A mutation in this gene could disrupt the process by which enamel and dentin are formed, potentially leading to a lack of these tissues. Thus, the correct answer to the question is option 'a'.
It is important to note that the other genes listed (keratin, collagen, and enamelase) are not directly involved in the initial production of enamel or dentin. Keratin is a protein found primarily in the skin, hair, and nails. Collagen is a major structural protein in connective tissues. Enamelase is a hypothetical enzyme that would break down enamel rather than participate in its production.