Meiosis occurs only after the onset of puberty while mitosis occurs throughout an entire lifetime.

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Generating the recurring cellular associations that define the cycle of the seminiferous epithelium. The cycle is generated by the precisely timed transition of A spermatogonia (red) into A1 spermatogonia (teal). In the mouse this transition occurs every 8.6 days. In addition, it takes 8.6 days for the A1 spermatogonia to become preleptotene spermatocytes (green) and enter meiosis and an additional 8.6 days ×3 to form elongated spermatids ready for spermiation. The net result is that once fully established the same cell associations or the same group of cell types appear every 8.6 days. In the 8.6-day period between the transition of A spermatogonia to A1 spermatogonia, there is a continuum of development of each cell type. Red, undifferentiated A spermatogonia; blue, differentiating A1 spermatogonia; green, preleptotene spermatocytes; purple, pachytene spermatocytes; orange, round or elongating spermatids; blue, elongated spermatids.

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