Interphase

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Interphase is the phase of the cell cycle in which a typical cell spends most of its life. During this phase, the cell copies its DNA in preparation for mitosis. Interphase is the 'daily living' or metabolic phase of the cell, in which the cell obtains nutrients and metabolizes them, grows, reads its DNA, and conducts other "normal" cell functions. The majority of eukaryotic cells spend most of their time in interphase. This phase was formerly called the resting phase. However, interphase does not describe a cell that is merely resting; rather, the cell is living, and preparing for later cell division, so the name was changed. A common misconception is that interphase is the first stage of mitosis. However, since mitosis is the division of the nucleus, prophase is actually the first stage.

In interphase, the cell gets itself ready for mitosis or meiosis. Somatic cells, or normal diploid cells of the body, go through mitosis in order to reproduce themselves through cell division, whereas diploid germ cells (i.e., primary spermatocytes and primary oocytes) go through meiosis in order to create haploid gametes (i.e., sperm and ova) for the purpose of sexual reproduction. Chromosomes are copied.

Video Interphase

Stages of interphase

There are three stages of cellular interphase, with each phase ending when a cellular checkpoint checks the accuracy of the stage's completion before proceeding to the next. The stages of interphase are:

• G₁ (Gap 1), in which the cell grows and functions normally. During this time, a high amount of protein synthesis occurs and the cell grows (to about double its original size) - more organelles are produced and the volume of the cytoplasm increases. If the cell is not to divide again, it will enter G₀.
• Synthesis (S), in which the cell duplicates its DNA (via semiconservative replication).
• G₂ (Gap 2), in which the cell resumes its growth in preparation for division. The mitochondria divide and the cell continues to grow until mitosis begins. In plants, chloroplasts also divide during G2.
• In addition, some cells that do not divide often or ever, enter a stage called G₀ (Gap zero), which is either a stage separate from interphase or an extended G₁.

The duration of time spent in interphase and in each stage of interphase is variable and depends on both the type of cell and the species of organism it belongs to. Most cells of adult mammals spend about 24 hours in interphase; this accounts for about 90%-96% of the total time involved in cell division. Interphase includes G1, S, and G2 phases. Mitosis and cytokinesis, however, are separate from interphase. In G1 phase decision for cell division is taking place.

Maps Interphase

Interphase within sequences of cellular processes

Interphase and the cell cycle

When G₂ is completed, the cell enters a relatively brief period of nuclear and cellular division, composed of mitosis and cytokinesis, respectively. After the successful completion of mitosis and cytokinesis, both resulting daughter cells re-enter G₁ of interphase.

In the cell cycle, interphase is preceded by telophase and cytokinesis of the M phase. In alternative fashion, interphase is sometimes interrupted by G₀ phase, which, in some circumstances, may then end and be followed by the remaining stages of interphase. After the successful completion of the G₂ checkpoint, the final checkpoint in interphase, the cell proceeds to prophase, or in plants to preprophase, which is the first stage of mitosis.

G₀ phase is viewed as either an extended G₁ phase where the cell is neither dividing nor preparing to divide and or as a distinct quiescent stage which occurs outside of the cell cycle.

Interphase and other cellular processes

In gamete production interphase is succeeded by meiosis. In programmed cell death, interphase is followed or preempted by apoptosis.

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See also

• Prophase
• Prometaphase
• Metaphase
• Anaphase
• Telophase

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References

Source of article : Wikipedia