A 32-year-old man and his 30-year-old wife present to a fertility clinic after 2 years of unsuccessful attempts to conceive. The man has normal secondary sexual characteristics and a normal semen volume, but semen analysis reveals azoospermia (absence of sperm). Further evaluation shows normal testosterone and elevated follicle-stimulating hormone (FSH) levels. Genetic testing is ordered to assess for Y chromosome microdeletions. Which of the following Y chromosome regions is most commonly associated with azoospermia due to microdeletions in infertile men?
