During telophase, the final stage of cell division, chromosomes arrive at opposite ends of the cell and begin to decondense back into loose chromatin. A new nuclear envelope forms around each set of chromosomes, nucleoli reappear, and the cell prepares to physically split into two daughter cells. Telophase essentially reverses the changes that happened at the start of division, rebuilding the internal structures that were dismantled so the chromosomes could separate.
How Telophase Fits Into Cell Division
Cell division follows a sequence of phases: prophase, prometaphase, metaphase, anaphase, and finally telophase. During the earlier stages, the cell condenses its DNA into tightly packed chromosomes, breaks down its nucleus, lines the chromosomes up along the middle, and pulls the two copies apart. Telophase is where the cell starts putting itself back together. It overlaps with cytokinesis, the physical pinching or partitioning of the cell into two, though the two processes are technically distinct.
Chromosomes Decondense
By the time telophase begins, the separated chromosomes have been pulled to opposite poles of the cell by spindle fibers. Once they arrive, the chromosomes start to uncoil. During earlier phases, DNA was wound tightly so it could be moved without tangling. Now that movement is complete, the chromosomes relax back into a diffuse form called chromatin. This is important because genes can only be read and used by the cell when DNA is in this loosely packed state. Tightly condensed chromosomes are essentially silent, so decondensation is the first step toward restoring normal cell function.
The Nuclear Envelope Reforms
One of the most dramatic events of telophase is the reassembly of the nuclear envelope around each group of chromosomes. The nuclear envelope is a double membrane studded with pores that controls what enters and exits the nucleus. It was broken into small membrane fragments during prometaphase to give the spindle fibers access to the chromosomes.
During telophase, those membrane fragments are recruited back to the surface of the decondensing chromosomes. Proteins on the chromosome surfaces act as docking sites, and the membrane pieces fuse together to form a continuous double membrane. Nuclear pore complexes, the gateways that regulate molecular traffic in and out of the nucleus, are reassembled within this new envelope. The process is rapid: in many mammalian cells, a functional nucleus can be rebuilt in roughly 10 to 20 minutes.
The reformation of the nuclear envelope reestablishes a key boundary. It separates the genetic material from the rest of the cell, restoring the compartmentalization that allows the nucleus to control gene expression and protect DNA from enzymes in the cytoplasm.
Nucleoli Reappear
The nucleolus, a dense structure inside the nucleus responsible for building the components of ribosomes, disappears during prophase. During telophase, nucleoli reform at specific chromosome regions that contain the genes coding for ribosomal components. These regions are called nucleolar organizing regions. As the chromosomes decondense, these genes become active again and begin producing the molecular building blocks of ribosomes, causing the nucleolus to gradually reemerge as a visible structure. A cell can have more than one nucleolus depending on how many of these organizing regions its chromosomes carry.
The Spindle Breaks Down
The mitotic spindle, the network of protein fibers that pulled the chromosomes apart during anaphase, is no longer needed during telophase. The spindle fibers (made of protein tubes called microtubules) are disassembled, and their building blocks are recycled back into the cell’s general pool of structural proteins. This dismantling allows the cell’s internal skeleton to reorganize into the arrangement typical of a non-dividing cell, which looks quite different from the spindle-dominated architecture of a dividing one.
Cytokinesis Overlaps With Telophase
While telophase handles the nuclear rebuilding, cytokinesis handles the physical division of the cytoplasm. The two processes overlap in timing but work through different mechanisms.
In animal cells, a ring of contractile protein filaments assembles just beneath the cell membrane at the cell’s equator. This ring tightens like a drawstring, pinching the cell inward to create a cleavage furrow that deepens until the cell is split in two. Each daughter cell receives one of the newly formed nuclei along with roughly half the organelles and cytoplasm.
In plant cells, the process looks different because a rigid cell wall surrounds the outside of the cell. Instead of pinching inward, vesicles carrying cell wall materials gather along the middle of the cell and fuse together outward, forming a structure called the cell plate. The cell plate eventually extends to meet the existing cell wall, creating a new partition between the two daughter cells.
Telophase in Meiosis
Telophase also occurs during meiosis, the type of cell division that produces sex cells like sperm and eggs. Meiosis has two rounds of division, so there are two telophases.
During telophase I, homologous chromosome pairs (one from each parent) have been separated. The nuclear envelope may or may not fully reform depending on the organism. In some species, cells move almost immediately into the second division without completely rebuilding the nucleus. When the envelope does reform, it is transient.
Telophase II looks much more like mitotic telophase. The sister chromatids have been pulled apart, and now four haploid cells are produced, each with half the chromosome number of the original cell. Nuclear envelopes reform, chromosomes decondense, and cytokinesis divides each cell. The result is four genetically unique cells rather than the two identical cells produced by mitosis.
What the Daughter Cells Look Like
By the end of telophase and cytokinesis, each daughter cell has a fully enclosed nucleus containing a complete set of chromosomes (in mitosis) or a half set (in meiosis). The chromosomes are decondensed and ready for gene expression. Nucleoli are present and beginning to manufacture ribosomal components. The cells are smaller than the parent cell, typically about half the volume, and will need to grow and produce new proteins and organelles before they can divide again. This growth period is part of interphase, the long stretch between divisions where the cell carries out its normal functions and eventually copies its DNA in preparation for the next round of division.