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): During the diplotene stage of prophase I, X-shaped structures called chiasmata become clearly visible. Reason (R): Diplotene is characterised by the complete separation of recombined homologous chromosomes from each other, including at the sites of crossovers. In the light of the above statements,
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- BBoth (A) and (R) are true but (R) is not the correct explanation of (A)
- C(A) is true but (R) is false
- D(A) is false but (R) is true
Correct answer
C. (A) is true but (R) is false
Step-by-step solution
Assertion (A) is true. 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, which become clearly visible during this stage. Reason (R) is false. The recombined homologous chromosomes do not separate completely; they remain attached at the sites of crossovers. The separation occurs everywhere EXCEPT