Leptotene Stage: It is the first phase of Prophase I of meiosis I where the chromosomes appear to be thin thread like structures. In this stage, chromosomes become visible in the form of thread-like structures. Chromomeres, the beads-like structure can be seen. This stage is also known as the bouquet stage due to the specific alignment of chromosomes in the nucleus. Chromosomes converge to one side of the nucleus towards the centrosome. Duplication of centriole takes place and they move to opposite poles of the nucleus, where they undergo further duplication. Leptotene is followed by the zygotene stage.

Leptotene Stage

During this stage, the chromosomes attach themselves by their ends (telomeres) to the inner membrane of the nuclear envelope. At the transition to the zygotene stage the telomeres usually aggregate at a nuclear envelope sector, thereby forming a meiotic bouquet. Lateral (axial) elements of the synaptonemal complex are also formed.

Immediately after DNA damaging treatment (gamma irradiation) during male mouse meiosis, it is possible to distinguish two types of DNA repair response. From the leptotene stage to early pachytene, exogenous DNA damage triggers the massive presence of gammaH₂AX throughout the cell nucleus, which is associated with DNA repair mediated by the homologous recombination proteins DMC1 and RAD51. From mid-pachytene to diplotene the predominant DNA repair pathway is non-homologous end joining.

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By Team Learning Mantras