Spinal Bulbar Muscular Atrophy (Kennedy Disease, AR CAG, XR)

A 46-year-old man presents with a 5-year history of progressive proximal leg weakness, muscle cramps, and hand tremor. On examination, he has fasciculations over the chin, lips, and tongue, with tongue atrophy and dysarthria. He also reports erectile dysfunction and notes bilateral gynecomastia with small testes. Neurological examination reveals lower motor neuron signs with absent reflexes but NO upper motor neuron signs. Genetic testing reveals a CAG repeat expansion (46 repeats) in the androgen receptor gene on the structure marked **A** in the diagram. Which of the following best describes the chromosomal location and pathogenic mechanism of this mutation?