Answer:
The variation in cells produced by meiosis occurs because of crossing over that takes place during pachytene, a substage of Prophase I.
Step-by-step explanation:
Meiosis I is consist of four stages Propase I, Metaphase I, Anaphase I and Telophase I.
Prophase I of Meiosis I has five substages namely; Leptotene,Zygotene, Pachytene, Diplotene and Diakinesis.
Leptotene. Each chromosomes has two long threads of sister chromatids as result of replication during the S phase of the cycle.
Zygotene.The pairing of chromosomes begin. Pair of chromosomes are called homologous chromosomes.