The telophase it is the last division stage of mitosis and meiosis. It is after anaphase and precedes cytoplasmic division or cytokinesis. The characteristic feature that distinguishes and defines it is the formation of new nuclei.
Once the duplicated DNA was compacted (prophase), the bound sister chromatids migrated to the equator of the cell (metaphase). Once they were all gathered there, they lined up to be mobilized to the poles of the dividing cell during anaphase..
Finally, in order to divide and give rise to two cells, two nuclei must first be formed to protect DNA. This is precisely what happens during the telophase of mitosis..
Not that something very different happens, mechanistically speaking, during the telophases of meiosis I and meiosis II. But the materials that are received as "chromosomes" are very different..
In telophase I, the cell in meiosis receives only one set of duplicate homologues at each pole. That is, a single set of the chromosomal complement of the species with each chromosome formed by two sister chromatids joined by the centromere.
At the telophase of meiosis II, sister chromatids migrate poleward, and nuclei with a haploid number of chromosomes form. At the end of telophase, the chromosomes are no longer visible as compacted structures.
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In this section we will consider three defining aspects of telophases: the beginning of the formation of nucleoli, the decondensation of chromatin and the appearance of new nuclear envelopes..
In open mitoses, many small nucleoli are formed, which as the cycle progresses, coalesce and form the nucleoli typical of the species (which are not many). With events that were triggered during metaphase, the structural biogenesis of these organelles begins in telophase..
This is of great importance because in the nucleoli, among other things, the RNAs that are part of the ribosomes are synthesized. In ribosomes, the process of translation of messenger RNAs to produce proteins is carried out. And every cell, particularly new ones, needs to make proteins quickly..
By dividing, therefore, each new cell product of that division will be competent for the translation process and autonomous existence.
On the other hand, the chromatin that is inherited from anaphase is highly compacted. This must be decondensed in order to be able to organize it within the nuclei in formation in open mitoses..
The role of controlling chromatin decondensation in a dividing cell is played by a protein kinase called Aurora B. This enzyme restricts the decondensation process during anaphase, thus limiting it to the last phase of division or telophase. In fact, Aurora B is the protein that controls the transition from anaphase to telophase..
The other important aspect of the telophase, and that defines it, is the formation of the nuclear envelope. Let us remember that in open cell divisions, the nuclear envelope disappears to allow a free mobilization of the condensed chromatin. Now that the chromosomes have segregated, they must be grouped into a new nucleus per cell pole.
To generate a new nucleus, chromatin must interact with the proteins that will form the nuclear lamina, or laminins. The laminins, in turn, will serve as a bridge for the interaction with other proteins that will allow the formation of the nuclear lamina.
This will separate the chromatin into eu- and hetero-chromatin, allow the internal organization of the nucleus and help in the consolidation of the inner nuclear membrane..
Simultaneously, microtubule structures derived from the endoplasmic reticulum of the stem cell will migrate to the condensation zone of telophase chromatin. They will cover it in small patches, and then coalesce to cover it completely.
This is the externam nuclear membrane which is continuous with the endoplasmic reticulum, and with the inner nuclear membrane..
All of the above steps describe the telophase of mitosis in their fundamentals. At each cell pole, a nucleus will be formed with the chromosomal complement of the mother cell..
But, unlike mitosis in animals, during mitosis in plant cells a unique structure known as a fragmoplast is formed. This appears between the two future nuclei in the transition between anaphase and telophase..
Its main role in plant mitotic division is to synthesize the cell plate. That is, the fragmoplast generates the site where the new cells of the plant will divide once telophase ends..
In meiotic telophases, what has already been described occurs, but with some differences. In telophase I, "nuclei" are formed with a single set of homologous (duplicated) chromosomes. Nuclei are formed in telophase II with a haploid complement of sister chromatids.
In many organisms, chromatin condensation does not occur at telophase I, which passes almost immediately to meiosis II. In other cases, the chromatin does decondense, but it quickly compacts again during prophase II..
The nuclear envelope is usually short-lived in telophase I, but permanent in II. The Aurora B protein controls the segregation of homologous chromosomes during telophase I. However, it does not participate in the segregation of sister chromatids during telophase II..
In all cases of nuclear division, this process is followed by one of division of the cytoplasm, a process called cytokinesis. Cytokinesis is observed both at the end of telophase in mitosis, and at the end of telophase I and telophase II of meiosis.
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