Familial Wilms Tumor WT1 Autosomal Dominant

A 3-year-old boy presents with a left-sided abdominal mass, hypospadias, cryptorchidism, and proteinuria with microscopic hematuria. Imaging reveals a 9 cm left renal mass consistent with Wilms tumor, and two small contralateral lesions raising concern for bilateral disease. A three-generation pedigree shows his father and older brother also had Wilms tumors in childhood with similar genitourinary anomalies, and his paternal grandmother had a childhood nephrectomy. The inheritance pattern shown in the pedigree, marked as **A**, demonstrates which of the following characteristics?