Undifferentiated germ cells, spermatogonia, undergo mitosis to form primary spermatocytes. These mitotic divisions do not produce exact clones, so primary spermatocytes are somewhat differentiated from spermatogonia. The first meiotic division of primary spermatocytes leads to secondary spermatocytes. Secondary spermatocytes undergo the second meiotic division and produce spermatids. Spermatids undergo differentiation to yield spermatozoa. This differentiation process of spermatids into spermatozoa includes elongation and the covering of the tip of the nucleus by the acrosome, an enzyme containing vesicle that plays a roll in penetration of the ovum.