1.A.L. is a healthy toddler with a normal perinatal history. Her parents notice a white spot in the pupil of one eye and request a referral to a pediatric ophthalmologist. Examination of the eye...

1.A.L. is a healthy toddler with a normal perinatal history. Her parents notice a white spot in the pupil of one eye and request a referral to a pediatric ophthalmologist. Examination of the eye suggests that A.L. has developed a retinoblastoma, a cancer in her eye. This cancer occurs in approximately 1 in every 1500 live births and approximately 250 children are diagnosed each year in the United States. The family is referred for genetic testing and counseling. Retinoblastoma can occur because of a change in chromosome 13 or a mutation in the RB 1 gene, which in its normal state prevents abnormal mitosis. A.L.’s tumor results from mutation of the RB1 gene, but neither parent shows this mutation.

(1)What is the difference in the cause and inheritance of chromosomal changes compared with the inheritance of a mutation in a specific gene?

(2)How did the mutation likely occur in the genes in A.L.’s tumor cells?

(3)Testing of A.L.’s blood shows no evidence of the RB1 mutation; how likely is it that A.L. could transmit the mutated gene to her children?

(4)How has the mutation caused growth of the tumor in A.L.’s eye?

(5) What is the prognosis if the tumor is limited to the intraocular tissues?