Video
by Expii
Having trouble remembering the steps to the cell cycle? We teamed up with Dwayne Reed, a creative Chicago teacher and rapper, to bring you a biology song worthy of the Billboard Hot 100.
Watch to the end to see how interphase, prophase, metaphase, anaphase, telophase, and cytokinesis work in harmony to help cell division.
Illustrated · 2 min
An adult human body has about 30 to 40 trillion cells, and every minute 300 million of those cells die.
The cell cycle is a series of stages that a cell must go through as it grows and divides. It allows new cells to replace old or dying cells. It also allows an organism to grow and develop.
The stages of the cycle in eukaryotic cells can be divided into two main parts: interphase and cell division.
Interphase is the period between cell divisions. It is the longest part of the cycle and can be thought of as the parent cell preparing for division. Interphase can be further divided into three phases: G, S, and G.
G Phase: Cell growth
During this first stage of interphase, the cell grows and produces more organelles and proteins. The G in this phase stands for "gap". Before moving on, the cell has to pass the G checkpoint, which makes sure there are enough resources within the cell to divide. Without this restriction point, cells could grow wildly, which could lead to cancer.
S Phase: DNA replication
During S phase, chromosomes in the nucleus are replicated. The S stands for DNA synthesis.
Normally, our cells are diploid, or 2n, meaning that they contain two sets of chromosomes. This makes sense because you get a set from each of your parents. During this phase, the cell makes another copy of each chromosome. We still call the cell diploid because it doesn't contain any new genetic information, just identical copies of what it already had. If you're confused, don't worry. We will go over this stage in more detail later.
G Phase: Preparing for cell division
During the last stage of interphase, the cell produces the organelles it will need for cell division. It also passes through the G checkpoint, checking for translation errors. The G in this phase also stands for "gap".
Sometimes cells enter what is called G phase. These cells are no longer dividing, often because they are completely developed and specialized.
Cell division is called the M phase (or mitotic phase) and consists of mitosis and cytokinesis.
Mitosis is the process during which replicated genetic material is segregated into two new cells. It consists of prophase, metaphase, anaphase, and telophase. These phases are explained in more detail in further sections.
Cytokinesis is a stage following mitosis. This is where the cytoplasm of the cell is actually split into two new cells. The new cells are called daughter cells.
The cycle repeats for the new cells.
Image source: By George Weller CC BY-SA 3.0, via Wikimedia Commons
Video
by Teacher's Pet
Cells are constantly dying, so how do our bodies keep up our cell count? We make more, of course. Watch this video to see how cells make more cells. You'll also learn some important vocabulary like chromosomes, mitosis, and cytokinesis.
Interactive · 2 questions
Have you ever wondered how cells produce more cells?
From Cell Theory, we know that all cells come from other existing cells. They do this by going through the cell cycle. This cycle is the time between the beginning of one cell division until the beginning of the next cell division. During this time, the cell grows, prepares for division, and then it divides to form daughter cells. From here, the cycle repeats.
Prokaryotic and eukaryotic cells have different ways of dividing.
Prokaryotes use something called binary fission, which is a lot simpler than the eukaryotic method of division. However, we are mostly concerned with how eukaryotic cells divide.
Image source: By JWSchmidt, JTojnar CC BY 3.0, via Wikimedia Commons
In eukaryotes (like plant and animal cells), the cell cycle is made up of two main parts: interphase and cell division. Interphase has three parts: the first gap phase (G), the synthesis phase (S), and the second gap phase (G).
Image source: By CNX OpenStax CC BY 4.0, via Wikimedia Commons
What are the three parts of interphase?
Cell division takes one of two forms depending on which type of cell is dividing. This step is often called the M phase because both types start with an M: mitosis and meiosis. M phase is followed directly by cytokinesis, which is the actual splitting of the cell.
Image source: By WikiES CC BY-SA 4.0, via Wikimedia Commons
Mitosis is what most cells in your body do. After a cell divides, there are two daughter cells that are identical to the original. The cells that go through mitosis and their daughter cells are called diploid cells. The steps of mitosis are prophase, metaphase, anaphase, and telophase.
Meiosis only occurs in sex cells. This is how individuals inherit traits from both of their parents. It creates four haploid sex cells, which have only half the normal number of chromosomes. The steps of meiosis are identical to those of mitosis, except the cell goes through two rounds of division—meiosis I and meiosis II.
What kind of cell division happens in sex cells?
Regulation of the cell cycle is super important. If part of the cycle goes wrong, then the cell might begin to divide uncontrollably. Unregulated cell growth and division is called cancer. This is why there are several checkpoints throughout the cycle to make sure everything is going according to plan.
: The steps cells go through in order to grow and divide
: The longest part of the cell cycle where the cell grows and DNA is replicated to prepare for nuclear division
: The process of dividing the nucleus
: The process of dividing one nucleus into two identical nuclei. Occurs in all cells except for sex cells
: The process of dividing one nucleus into four unique haploid cells. Only occurs in sex cells
: The final step of cell division where the cytoplasm is divided to form daughter cells
: Cells that contain two sets of chromosomes
: Cells that contain only half the normal number of chromosomes. These are sperm and egg cells
