Question

Which of the following events precede reorganisation of the nuclear envelope during the M-phase of the cell cycle?

• A. Decondensation of chromosomes and reorganisation of nuclear lamina
• B. Transcription of chromosomes and reorganisation of nuclear lamina
• C. Formation of phragmoplast and contractile ring
• D. Transcription of chromosomes and formation of the contractile rings

Answer 1

The correct option is A Decondensation of chromosomes and reorganisation of nuclear lamina

Cell division comprises of different phases such as prophase, metaphase, anaphase, telophase and finally cytokinesis.

M-phase is mitotic phase and cell division occurs in this phase. Reorganisation of the nuclear envelope during the M-phase of the cell cycle takes place during telophase.

The statement "Transcription of chromosomes and reorganisation of nuclear lamina" is wrong since all transcription is stopped during the mitotic phase. Transcription only begins once the M phase ends and interphase starts again.

"Formation of phragmoplast and contractile ring" is wrong since phragmoplast (bundle of microtubules that help in the formation of cell wall during cytokinesis in plant cells) and contractile ring (a ring of microtubules that contracts during cytokinesis) are both formed after the M phase in the cytokinesis stage.

The statement "Transcription of chromosomes and formation of the contractile rings" is wrong since both take place after the M phase and not before.

The statement "Decondensation of chromosomes and reorganisation of nuclear lamina" is true since nuclear lamina has to be reorganised for the nuclear envelope to form and the decondensation of chromosomes starts during the telophase right before the reappearance of the nuclear envelope.