Cells in G 0 phase are not actively preparing to divide. The cell is in a quiescent inactive stage that occurs when cells exit the cell cycle. Some cells enter G 0 temporarily until an external signal triggers the onset of G 1. Other cells that never or rarely divide, such as mature cardiac muscle and nerve cells, remain in G 0 permanently.
Privacy Policy. Skip to main content. Cell Reproduction. Search for:. The Cell Cycle. Interphase Cells must grow and duplicate their internal structures during interphase before they can divide during mitosis.
Learning Objectives Describe the events that occur during Interphase. Cells spend most of their lives in interphase, specifically in the S phase where genetic material must be copied. 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.
The Mitotic Phase and the G0 Phase During the multistep mitotic phase, the cell nucleus divides, and the cell components split into two identical daughter cells. Learning Objectives Describe the events that occur at the different stages of mitosis. Key Takeaways Key Points During prophase, the nucleus disappears, spindle fibers form, and DNA condenses into chromosomes sister chromatids.
During metaphase, the sister chromatids align along the equator of the cell by attaching their centromeres to the spindle fibers. During anaphase, sister chromatids are separated at the centromere and are pulled towards opposite poles of the cell by the mitotic spindle. During telophase, chromosomes arrive at opposite poles and unwind into thin strands of DNA, the spindle fibers disappear, and the nuclear membrane reappears.
Cytokinesis is the actual splitting of the cell membrane; animal cells pinch apart, while plant cells form a cell plate that becomes the new cell wall. Many single-celled organisms reproduce by cell division and have a single copy of each chromosome. Virtual Genetics Education Centre. Within the tetrad, any pair of chromatid arms can overlap and fuse in a process called crossing-over or recombination.
Recombination is a process that breaks, recombines and rejoins sections of DNA to produce new combinations of genes. In metaphase I, the homologous pairs of chromosomes align on either side of the equatorial plate. Then, in anaphase I, the spindle fibers contract and pull the homologous pairs, each with two chromatids, away from each other and toward each pole of the cell.
During telophase I, the chromosomes are enclosed in nuclei. The cell now undergoes a process called cytokinesis that divides the cytoplasm of the original cell into two daughter cells. Each daughter cell is haploid and has only one set of chromosomes, or half the total number of chromosomes of the original cell.
Meiosis II is a mitotic division of each of the haploid cells produced in meiosis I. During prophase II, the chromosomes condense, and a new set of spindle fibers forms. The chromosomes begin moving toward the equator of the cell.
Open survey. In: Facts In the Cell. In metaphase individual chromosomes pairs of chromatids line up along the equator. During anaphase the sister chromatids are separated to opposite poles. During anaphase I the sister chromatids move together to the same pole. During anaphase II the sister chromatids are separated to opposite poles.
Similarities Mitosis Diploid parent cell Consists of interphase, prophase, metaphase, anaphase and telophase In metaphase individual chromosomes pairs of chromatids line up along the equator. Ends with cytokinesis.
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