A 2 year old girl is evaluated because of deteriorating vision. On physical examination, a whitish hue is noted in the right pupil, along with strabismus. Palpation of the eye elicits apparent pain and tenderness. The patient is referred to an ophthalmologist, who schedules surgery, and removes a multifocal tumor from the right eye. The pathology repo notes the presence of rosettes composed of cuboidal-to-columnar cells surrounding a central lumen in the tumor. In all likelihood, this child's condition stems from a mutation in a gene on chromosome ?