AZFc deletions in the long arm of the human Y chromosome (Yq11.23) are the most frequent known genetic lesion causing male infertility, leading to azoospermia or severe oligozoospermia with a frequency of 10-20% of infertile men from different populations. The AZFc sequence is mainly composed of large repeated sequence blocks called amplicons, organized into palindromic structures showing high (>99.9%) sequence homology between the arms. Such structures may undergo frequent rearrangements including inversions, duplications and deletions. The AZFc deletions are produced by intrachromosomal recombination events between some of these amplicons.

AZFc contains eight gene families expressed only in testis tissue, three of them coding for proteins, but the importance of each gene for fertility is not yet understood. We addressed the question of functionality to the multi-copy DAZ gene family in AZFc, analyzing its putative functional redundancy by studying DAZ gene diversity in normal fertile and infertile men with severe oligozoospermia.