The cell grows and carries out biochemical functions, such as protein synthesis, in the G 1 phase. During the S phase, DNA is duplicated into two sister chromatids, and centrosomes, which give rise to the mitotic spindle, are also replicated. In the G 2 phase, energy is replenished, new proteins are synthesized, the cytoskeleton is dismantled, and additional growth occurs. Key Terms interphase : the stage in the life cycle of a cell where the cell grows and DNA is replicated sister chromatid : either of the two identical strands of a chromosome DNA material that separate during mitosis mitotic spindle : the apparatus that orchestrates the movement of chromosomes during mitosis.
Interphase During interphase, the cell undergoes normal growth processes while also preparing for cell division. During interphase, the cell grows and the nuclear DNA is duplicated. Interphase is followed by the mitotic phase. During the mitotic phase, the duplicated chromosomes are segregated and distributed into daughter nuclei.
This can be explained by the fact that G1 follows cell division in mitosis; G1 represents the first chance for new cells have to grow. Cells usually remain in G1 for about 10 hours of the 24 total hours of the cell cycle. The length of S phase varies according to the total DNA that the particular cell contains; the rate of synthesis of DNA is fairly constant between cells and species.
Usually, cells will take between 5 and 6 hours to complete S phase. G2 is shorter, lasting only 3 to 4 hours in most cells. In sum, then, interphase generally takes between 18 and 20 hours. Mitosis, during which the cell makes preparations for and completes cell division only takes about 2 hours. It is possible to determine the time a cell spends in different phases of the cell cycle and its specific location in the cycle by feeding cells with molecules that are only taken into the cell at a specific point in the cell cycle.
At the end of prophase the membrane around the nucleus in the cell dissolves away releasing the chromosomes. The mitotic spindle, consisting of the microtubules and other proteins, extends across the cell between the centrioles as they move to opposite poles of the cell. Metaphase: The chromosomes line up neatly end-to-end along the centre equator of the cell.
The centrioles are now at opposite poles of the cell with the mitotic spindle fibres extending from them. The mitotic spindle fibres attach to each of the sister chromatids. Anaphase: The sister chromatids are then pulled apart by the mitotic spindle which pulls one chromatid to one pole and the other chromatid to the opposite pole.
Telophase: At each pole of the cell a full set of chromosomes gather together. A membrane forms around each set of chromosomes to create two new nuclei. The single cell then pinches in the middle to form two separate daughter cells each containing a full set of chromosomes within a nucleus. This process is known as cytokinesis. Related Content:. What is a stem cell?
What is a cell? What is DNA? This part of the root elongates and grows, so these cells are actively dividing. The blastula is a very early stage in embryonic development, so a lot of mitosis must occur in order for the blastula to grow into a baby whitefish. Notice that the chromatin is spread throughout the nucleus, and the nucleolus is visible. In prophase, the chromatin has condensed into chromosomes, and the nucleolus has disappeared.
In metaphase, the chromosomes are lined up along the metaphase plate. We can also see the mitotic spindle! In anaphase, the sister chromatids are moving toward opposite poles.
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