Final answer:
The mitosis stage where chromosomes decondense and lengthen is telophase. It marks the end of mitosis, with mitotic spindles breaking down and nuclear envelopes reforming around chromosomes, followed by cytokinesis dividing the cytoplasm into two daughter cells.
Step-by-step explanation:
The stage of mitosis in which the chromosomes begin to decondense and lengthen is known as telophase. During telophase, various processes that occurred in the earlier stages of mitosis are reversed. Chromosomes that have arrived at the opposite poles of the cell begin to unravel, transitioning from their condensed, visible state back into a less condensed chromatin configuration. Concurrently, mitotic spindles are depolymerized into tubulin monomers, which are then repurposed to construct the cytoskeletal components for each of the daughter cells. Moreover, nuclear envelopes start to re-form around the chromosomes, which marks the preparation for the eventual re-establishment of fully functional nuclei.
While telophase signals the end of mitosis, it is followed by cytokinesis, which is the process of dividing the cytoplasm, finally resulting in two separate daughter cells. This sequential process ensures that each daughter cell inherits the correct number of chromosomes and is ready to begin interphase, which is the phase of the cell cycle where the cell grows and prepares for the next round of mitosis.