1
Which one of the following precedes reformation of the nuclear envelope during M phase of the cell cycle?
- Decondensation from chromosomes, and reassembly of the nuclear lamina
- Transcription from chromosomes, and reassembly of the nuclear lamina
- Formation of the contractile ring, and formation of the phragmoplast
- Formation of the contractile ring, and transcription from chromosomes
Answer
(3) Formation of the contractile ring, and formation of the phragmoplast
Solution
As per NCERT, in animal cells cytokinesis is achieved by a furrow in the plasma membrane, and in plant cells by the cell plate; cytokinesis usually begins in late anaphase/telophase.
⇒ The contractile ring (animal cells) and the phragmoplast (plant cells) begin to form in late anaphase, before the nuclear envelope reforms around the chromosome clusters in telophase.
∵ Reassembly of the nuclear lamina is itself part of the reformation of the nuclear envelope, and decondensation of chromosomes and resumption of transcription follow it, they cannot precede it.
Answer: (3)
AIPMT 2004