Final answer:
The gene on the Y chromosome responsible for determining maleness is called SRY gene.
Step-by-step explanation:
The gene on the Y chromosome in humans responsible for determining maleness is called SRY (sex-determining region Y) gene. This gene encodes a transcription factor that triggers the development of male sex characteristics during embryonic development. Without the SRY gene, an individual will develop into a female, as females do not have a Y chromosome.