Which one of the following precedes reformation of the nuclear envelope during Mphase of the cell cycle?
(a) Decondensation from chromosomes and reassembly of the nuclear lamina.
(b) Transcription from chromosomes and reassembly of the nuclear lamina.
(c) Formation of the contractile ring and formation of the phragmoplast.
(d) Formation of the contractile ring and transcription from chromosomes.
(a) Decondensation from chromosomes and reassembly of the nuclear lamina.
Explanation:
In most eukaryotes, the nuclear envelope that separates the DNA from the cytoplasm disassembles. The chromosomes align themselves in a line spanning the cell. Microtubules, essentially miniature strings, pulls out from opposite ends of the cell and shorten, pulling apart the sister chromatids of each chromosome. As a matter of convention, each sister chromatid is now considered a chromosome, so they are renamed to sister chromosomes. As the cell elongates, corresponding sister chromosomes are pulled toward opposite ends. A new nuclear envelope forms around the separated sister chromosomes.