With the help of suitable diagrams, explain the five stages of prophase I of meiosis.

Explanation

(i) Prophase I is the most important stage of meiosis and differs considerably from the prophase of mitosis. (ii) It is divided into 5 stages leptotene, zygotene , pachytene , diplotene and diakinesis . (iii) It involves essentially the crossing over and recombination of gentic material between non sister chromatids.
(iv) Phase - I - Leptotene : In this stage already replicated chromatin network condenses and start converting into long thin thread like chromosomes.
(v) Phase - II - Zygotene : In this stage homologous chromosomes come closer to each other. This pairing is called 'Synapsis'.
(vi) Phase - III - Pachytene : Sister chromatids become visible in this stage. Crossing over occurs between non-sister chromatids of the homologous chromosomes . The crossing over is called as 'Chiasmata ' and this leads to genetic recombination causing variations.
(vii) Phase - IV - Diplotene : In this stage , recombined sister chromatids start repelling . Nucleolus and nuclear membrane start disappearing.
(viii) Phase - V - Diakinesis : Chromosomes further condense and shorten . Nucleolus and nuclear membrane completely disappear , spindle fibres begin to appear.