2004 AIPMT Cell Cycle and Cell DivisionM Phase: Telophase and Cytokinesis Hard Question 80 of 87 in Cell Cycle and Cell Division

Which one of the following precedes re-formation of the nuclear envelope during M phase of the cell cycle :-

A Transcription from chromosomes and reassembly of the nuclear lamina
B Formation of the contractile ring and formation of the phragmoplast
C Formation of the contractile ring and transcription from chromosomes
D Decondensation from chromosomes and reassembly of the nuclear lamina

The answer is B.

Solution

During M phase, the nuclear envelope breaks down at the end of prophase and is re-formed around each group of chromosomes in telophase.
The contractile ring of actin and myosin filaments (in animal cells) is assembled at the equator of the cell during anaphase, when the position of the future cleavage furrow is decided by the spindle.
In plant cells, the phragmoplast (an array of microtubules where the cell plate will form) also begins to form between the separating chromosome groups in late anaphase.
So formation of the contractile ring and formation of the phragmoplast begin before the nuclear envelope re-forms in telophase.
Decondensation of chromosomes, reassembly of the nuclear lamina (by dephosphorylation of lamins) and resumption of transcription go along with or after the re-formation of the nuclear envelope, as the nucleus returns to interphase.
So formation of the contractile ring and formation of the phragmoplast precede re-formation of the nuclear envelope.

Concept Order of events at the end of mitosis

Cell Cycle and Cell Division in past papers

87 questions from this chapter have appeared across 23 exam years.