The S phase of the cell cycle occurs during interphase, prior to mitosis or meiosis, and is in charge of DNA synthesis or replication. A cell's genetic material is therefore doubled before entering mitosis or meiosis, allowing enough DNA to be divided into daughter cells. The S phase can be further subdivided into G1 phase and G2 phase.
During G1 phase, the cell grows and reproduces itself using the DNA it has inherited from its parent cells. Cell division occurs during mitosis, which is when the nuclear membrane breaks down and the chromosomes are distributed between the two daughter cells. During this process, each chromosome is copied into two identical copies, one for each daughter cell. The S phase and G2 phase occur before mitosis, while M phase occurs during mitosis.
In conclusion, the S phase of the cell cycle allows for the duplication of the genome before dividing into two daughter cells. This occurs every time a cell divides to make more cells. Some cells (such as blood cells) may divide many times before they die. Other cells (such as neurons) do not divide again after their first division because they use up their entire lifetime supply of DNA in that single cell. Neurons therefore require careful management by the body to get enough new cells to replace those that are lost through death or aging.
A diagram illustrating the cell cycle Interphase is made up of the G1 phase (cell growth), the S phase (DNA synthesis), and the G2 phase (cell growth). At the completion of interphase, the mitotic phase begins, which consists of mitosis and cytokinesis and results in the production of two daughter cells. The duration of each phase varies depending on the type of cell.
Cells grow and divide throughout their lifetime. Every time a cell divides it creates two new cells that are identical to the original cell except for the number of times they have divided. This process is called division or replication. Healthy cells usually divide twice per day, producing four new cells with the same DNA content as the original cell. Unhealthy cancer cells often divide more frequently than this, causing them to reproduce faster than healthy cells. As a result, large numbers of cancer cells are produced by a single tumor cell that has escaped from its bed into the surrounding tissue where it can grow into another mass. These newly formed cells may also leave the primary site and invade other parts of the body where they continue to grow into secondary tumors. Tumors may also metastasize when cells break away from a primary tumor and spread via the blood or lymph system to other parts of the body where they form secondary tumors. Cancer cells may also enter the bloodstream or lymphatic system without forming a tumor, but instead travel alone or in small groups of up to 500 cells known as "clumps".
During interphase, the cell develops and duplicates its DNA. During the mitotic (M) phase, the cell splits its cytoplasm and divides its DNA into two sets, resulting in the formation of two new cells. Interphase can be divided into three main periods: G1, S, and G2.
In G1, the cell grows and prepares itself for division by copying some of its DNA into molecules called ribonucleic acids or RNAs. It also increases in size due to an accumulation of proteins that will be needed for cell division. The primary function of G1 is to make copies of the genome. After about 24 hours, the cell enters the S phase when the genome is replicated again before the start of M phase.
In G2, the cell adjusts its shape and makes repairs to the DNA before splitting into two daughter cells. This process is known as cytokinesis. Cytokinesis involves the scission of intracellualr membranes to divide the cell into two parts. The second main period of interphase is called M phase, which begins with the breakdown of nuclear membranes and ends with the complete separation of chromosomes into the two new cells. Proteins are required for all stages of the cell cycle except M phase.
The cell cycle is repeated whenever the cell divides so that each daughter cell receives a copy of the genome.