NEETBotanyCell Cycle and Cell Division
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The X-shaped structures called chiasmata become visible during the diplotene stage of meiosis I. Reason (R): Dissolution of the synaptonemal complex occurs during diplotene, causing recombined homologous chromosomes of the bivalents to separate from each other except at the sites of crossovers. In
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
According to NCERT, the beginning of diplotene is recognised by the dissolution of the synaptonemal complex and the tendency of the recombined homologous chromosomes of the bivalents to separate from each other except at the sites of crossovers. These X-shaped structures are called chiasmata. Thus, the dissolution of the synaptonemal complex is the direct mechanical cause that allows the homologous chromosomes to pull apart, making the chiasmata (the points of attachment where crossing over occurred) clearly visibl