Definition of Leptotene
Leptotene is the first stage that happens in the prophase of meiosis I. Meiosis is the process of cell division in which the genetically diverse sex cells are formed. These sex cells are also termed as gametes which are haploid in number. Meiosis is composed of two divisions i.e. meiosis I and meiosis II which occur successively.
The first phase in meiosis I is prophase I which has further five substages namely leptotene, zygotene, pachytene, diplotene, and diakinesis. The chromosomes start getting condensed in the nucleus in order to form long strands. At this stage, the chromosomes become apparent. But the two sister chromatids of the chromosome are closely associated with each other and appear to be one and hence are indistinguishable.