In males, it is estimated that 10–15% of cases of azoopermia and oligozoospermia result from deletions within the Y chromosome, specifically the region which contains the DAZ gene cluster (Reijo et al., 1995), but DAZL is considered to be a prime candidate implicated in roughly 60% of idiopathic male infertility, given its high similarity to DAZ, its germ-cell specific expression and the suspected involvement of autosomal recessive mutations in these men (Lilford et al., 1994; Visser and Repping, 2010). The gene discussed is DAZ1; the disease is male infertility.