**3.3 In vitro gamete interaction tests**

During fertilization, a sperm initially binds to the oocyte zona pellucida (ZP), undergoes the acrosome reaction (AR), penetrates the ZP, and fuses with the oolemma to form a zygote. Sperm-ZP interactions are carbohydrate-mediated events in various species, including humans (Benoff, 1997). The ZP of mammalian oocytes is a critical site for sperm-oocyte interaction. The ability of sperm to bind to the ZP indicates many functions of spermatozoa, such as viability, motility, morphology, acrosomal status and the ability to penetrate the oocyte (Liu & Baker, 1994), and for that reason this ability is of a diagnostic relevance.
