Pachytene kalma ce da ake amfani da ita a cikin kwayoyin halitta kuma tana nufin mataki a cikin kashi na farko na meiotic na tantanin halitta. A wannan mataki, chromosomes masu kama da juna suna haɗuwa tare da musayar sassan kwayoyin halitta a cikin wani tsari da ake kira recombination homologue. Wannan tsari yana haifar da samuwar sababbin haɗuwar kwayoyin halitta akan chromosomes. Kalmar “pachytene” ta fito ne daga kalmomin Helenanci “pachys” ma’ana kauri, da kuma “tenos” ma’ana zare, tana nufin kauri na chromosomes da bayyanarsu a matsayin zaren lokacin wannan mataki na meiosis.