When is dna synthesis in the cell cycle

Some cells, such as blood cells in bone marrow , skin cells, and cells lining the stomach and intestines, divide rapidly and constantly. Other cells divide when needed to replaced damaged or dead cells. These cell types include cells of the kidneys , liver, and lungs. Still other cell types, including nerve cells , stop dividing once mature.

The two main divisions of the cell cycle are interphase and mitosis. During this segment of the cell cycle, a cell doubles its cytoplasm and synthesizes DNA.

It is estimated that a dividing cell spends about percent of its time in this phase. Stages of Mitosis. In mitosis and cytokinesis, the contents of the dividing cell are equally distributed between two daughter cells. Mitosis has four phases: Prophase, Metaphase, Anaphase, and Telophase.

Once a cell has completed the cell cycle, it goes back into the G 1 phase and repeats the cycle again. Cells in the body can also be placed in a non-dividing state called the Gap 0 phase G 0 at any point in their life. Cells may remain in this stage for very long periods of time until they are signaled to progress through the cell cycle as initiated by the presence of certain growth factors or other signals. Cells that contain genetic mutations are permanently placed in the G 0 phase to ensure that they are not replicated.

When the cell cycle goes wrong, normal cell growth is lost. Cancer cells may develop, which gain control of their own growth signals and continue to multiply unchecked. Not all cells divide through the process of mitosis. Organisms that reproduce sexually also undergo a type of cell division called meiosis. Meiosis occurs in sex cells and is similar in process to mitosis. After a complete cell cycle in meiosis, however, four daughter cells are produced. Each cell contains one-half the number of chromosomes as the original parent cell.

This means that sex cells are haploid cells. The premeiotic synthesis of DNA takes place in primary spermatocytes during the resting phase and terminates just before the visible onset of the meiotic prophase.

Its average duration is 14 hours. No further synthesis of DNA takes place in later stages of spermatogenesis. Copyright and License information Disclaimer. Copyright notice. This article has been cited by other articles in PMC.

Full text Full text is available as a scanned copy of the original print version. Mutat Res. Biophys J.

Synthesis of deoxyribonucleic acid during the division cycle of bacteria. Pattern of synthesis of deoxyribonucleic acid in Bacillus cereus growing synchronously out of spores. Thymine deficiency and the normal DNA replication cycle.