Question: 137: Identify the correct sequence of events during Prophase I of meiosis :
(a) Synapsis of homologous chromosomes
(b) Chromosomes become gradually visible under microscope
(c) Crossing over between non-sister chromatids of homologous chromosomes
(d) Terminalisation of chiasmata
(e) Dissolution of synaptonemal complex
Choose the correct answer from the options given below :
(1) (a), (b), (c), (d), (e)
(2) (b), (c), (d), (e), (a)
(3) (b), (a), (c), (e), (d)
(4) (a), (c), (d), (e), (b)
Answer: Option (3)
Explanation:
Prophase I of meiosis is a long phase divided into leptotene, zygotene, pachytene, diplotene, and diakinesis.
In leptotene stage, chromosomes start condensing and become gradually visible under the microscope, which corresponds to statement (b).
In zygotene stage, synapsis of homologous chromosomes occurs with the formation of the synaptonemal complex, corresponding to statement (a).
In pachytene stage, crossing over takes place between non-sister chromatids of homologous chromosomes, corresponding to statement (c).
In diplotene stage, the synaptonemal complex dissolves and homologous chromosomes start separating except at chiasmata, corresponding to statement (e).
In diakinesis stage, terminalisation of chiasmata occurs, corresponding to statement (d).
Therefore, the correct sequence of events is (b), (a), (c), (e), (d).