the cell cycle refers to the events that sematic cells which includes all of the cells in our bodies except the reproductive cells go through from the moment they're formed until the moment they divide into two identical daughter cells this cycle varies in length depending on the type of cell for rapidly dividing cells like skin cells it takes less than a day whereas for other cells like liver cells the cell cycle can last years the cell cycle has two phases innerphase and mitosis inner phase is the longest part of the cell cycle and it's a state of preparation during which the cell carries out its cell functions and grows and replicates its DNA to prepare for mitosis or cellular division after a parent cell divides each of the two daughter cells enter innerphase again now interface can be broken down into three subf G1 s and G2 G1 stands for Gap or growth one and it's the longest phase of the cell cycle during G1 the cell mostly grows and the organel take care of regular cellular business like the synthesizing of proteins and producing energy inside the cell nucleus there's our DNA organized as chromosomes and during G1 each chromosome is made up of a single thin spaghetti of DNA called a chromatid at the end of G1 there's a cell cycle control Point called the G1 checkpoint where the cell checks to see if the DNA is not damaged and it synthesized the right proteins in the correct amount if it turns out that there is any reason for the cell not to divide like having DNA damage things can go one of two ways the cell can either enter a non-dividing state called the g0 phase where the DNA repair mechanisms try to fix the problem or the cell can self-destruct in a process called apoptosis now if the cell does get the go-ahead at the G1 checkpoint it enters the S phase s stands for synthesis because during this phase DNA is replicated so that each daughter cell receives identical copies of the genetic material so for each chromosome from G1 an identical copy is created this happens with the help of a number of proteins both structural proteins and enzymes as well as energy now just to be clear this doesn't mean that the number of chromosomes increases human sematic cells have 46 chromosomes throughout the cell cycle the amount of DNA they have though and in turn their aspect changes throughout the cell cycle so each chromosome enters the s-phase with a single copy of the genetic information called a chromatid during replication each chromatid is copied and pasted so the amount of DNA doubles up the two resulting chromatids are identical to each other and to the original genetic temp template and they join together in the center in a region called the centrom miror but they still make up a single chromosome so while the amount of genetic information is doubled there are still 46 chromosomes that contain the genetic information the cell can now enter the G2 phase G2 stands for Gap or growth too even after synthesizing copies of the DNA the cell still has to duplicate organel so that there are enough for both daughter cells in fact by the end of G2 the cell looks like a big balloon of cytoplasm in organel just waiting to split before it can do that though it has to first pass the final G2 checkpoint and if there's no DNA damage after replication the cell can enter mitosis now mitosis is when it actually divides into two daughter cells and it involves separating the replicated DNA in two distinct nuclei a process called Kinesis and the actual separation of the daughter cells into two distinct cells a process called cytokinesis mitosis can also be broken down into four subphases in order these are the prophase the metaphase the anaphase and the tase and they're immediately followed by cyto canis you can remember this with the pneumonic please make another two cells during prophase the membrane around the nucleus disintegrates and the chromosomes condense and become visible under a microscope like 46 Little X shapes the condensed sister chromatids make even the tiny Y chromosome in a male look like an X inside the cytoplasm two organel called the centrosomes migrate to opposite poles of the cell during metaphase chromosomes move toward the middle of the cell on a line called the metaphase plate so think M for metaphase and M for Middle when the chromosomes are in place each centrosome sends out threadlike ejections called spindle fibers that attach to the central mirror of each chromosome next during anaphase the croome start pulling on the spindle fibers to pull the sister chromatids apart like a game of tug ofwar since both centrosomes pull with equal force in opposite directions eventually the cister chromatids separate and reach the opposite poles of the cell finally there's the tilo phase during which a nuclear membrane forms around each new set of four 36 single chromatid chromosomes after that during cyto canis the cell membrane pinches in until the two daughter cells separate now both those daughter cells can enter the cell cycle once more if they need to if they don't they enter the non-dividing or g0 phase g0 is considered to be a phase outside the cell cycle because while the cells are living they're neither dividing nor preparing to divide an example example of this would be hepatocytes which rest in g0 until there's liver damage at which point they enter G1 again so that they can divide and replace damaged tissue another example would be neurons which spend their entire life in g0 all right as a quick recap the cell cycle can be divided into two phases innerphase and mitosis interphase comprises of the G1 phase during which the cell grows and performs its cell functions the S phase phase during which DNA is replicated and the G2 phase during which the cell grows again before entering mitosis mitosis can be broken down into prophase metaphase anaphase and tilas during which the replicated DNA divides equally for the two daughter cells and ends with cyto canis which is when the cell membrane actually divides to form the two new cells helping current and future clinicians f Focus learn retain and Thrive learn more