The cell cycle, or cell division cycle, is the life cycle of the cell. It's the series of events that take place leading up to the division of a cell into two daughter cells. The cell cycle consists of two stages, interphase and mitotic phase. The first stage involves the duplication of the cell and the second stage involves the division of the cell.
This first stage begins when the cell first forms. Eventually, that cell has to grow up so it can split and give birth to new cells. The interphase stage consists of three processes.
- G1 phase – During this phase, the cell grows and develops into a mature cell. The building blocks that it needs for the next stages during the cell cycle are forming at this time.
- S Phase – It is during the S phase that the cell duplicates the DNA in its nucleus. During this phase, the centrosome is also copied. The centrosome will be used later on during the cell cycle.
- G2 Phase – During this phase, the cell is preparing itself for mitosis. It is still growing and making proteins and organelles.
The G2 phase ends when the cell enters the mitotic stage. During this stage, the cell divides itself into two identical cells. The copied DNA is split between the two new cells. This phase consists of two different processes.
- Mitosis – During mitosis, the DNA of the cell is condensed and then splits. The split of the DNA and chromosomes are referred to as the mitotic spindle. Mitosis occurs in four phases: prophase, metaphase, anaphase and telophase.
- Cytokinesis – This is the process where the cell actually divids into two distinct cells. While the end results of cytokinesis are the same in plant and animal cells, the process that they take to get there are a little different.
The splitting of the cells is the end of the cell cycle for the original cell. It is also the beginning of the cell cycle for the new cells. The amount of time required for the cell cycle varies and depends on the cell type. Some cells will go through the cycle rapidly. Cells in the intestine are considered fast cycling cells, and can go through the process in less than 10 hours. Other cells are not as fast and can take longer. A typical cell will take about 24 hours to complete the cycle.
1. Zoom: Toddler in Kindergarten
Hot Spot: Green-Clothes = G
Learning: This CoursePic will discuss the cell cycle by talking about the education of a chrome-zombie, who represents a chromosome. Cells have to grow in order to create new cells. They do this copying their DNA and then splitting into two identical cells. In the first stage, the first gap phase, the cell starts to grow larger. This gap phase is represented by the gap-tooth the zombie has and by the green-clothes the zombie wears
Story: Craig the Chrome-zombie has high hopes for Kindergarten. He wears his favorite green-shirt and grins as he waves goodbye to his mom, showing off the gap-in-his-teeth.
2. Zoom: The Chrome Zombie is asleep in time out
Hot Spot: Sleeping-Zombie = Rest phase
Learning: If a cell is not ready to divide yet, it goes into the G0 or rest phase. Here, the cell isn’t actively copying its genetic material or doing anything else to prepare for cellular division. The sleeping-zombie represents the inactive cell
Story: But Kindergarten and Craig don’t get along so well. The little Chrome-Zombie has been put in time out for playing while he should have been studying for a test. He falls asleep while listening to the teacher drone on and on about how he’s not doing anything to help him learn or grow.
3. Zoom: Teenage Siamese twin zombies in the library
Hot Spot: Studying = S phase
Learning: In the S phase, the cell creates a copy of all of the genetic material in the nucleus. It duplicates its centrosome as well. This is the structure that organizes the microtubules and is needed in the next phase. This Chrome-Zombie is now a Siamese twin, with each half containing all of the DNA of the cell. She’s studying, which represents the S-phase.
Story: Craig begins to think that there must be a better way to work hard and play hard. By junior high, he has turned himself into Chrome-Zombie Siamese twins. Each half contains all of the knowledge and talents of the original, but now one can play full time while the other works. However, since they still have much more to learn before they can graduate, his working twin makes sure they spend a lot of time in the library studying. They call this their Studying Phase, or S Phase for short.
4. Zoom: Teen Siamese Chrome-Zombies is college
Hot Spot: Green-Tutu = G2 phase
Learning: During the G2 or second gap phase, the cell continues to grow. It produces additional organelles and proteins, and the contents of the cell are rearranged before going into mitosis. The zombie’s green-tutu and the second gap-in-its-teeth represent this phase.
Story: All the money his zombie mom would have invested in orthodontic work, Craig invested into making himself a twin, so now the Siamese Chrome-Zombies have developed a second gap-in-their-teeth, representing their G2 phase. They’re attending college now and have decided to study dance. After all, who’s looking at their teeth when they’ve got dance moves like this? They proudly show off their dance skills in their green-tutu.
5. Zoom: The Siamese Twin Zombie in a graduation gown
Hot Spot: My-toes = Mitosis
Learning: Mitosis is the final phase before cell division. During this phase, the DNA in the nucleus condenses, becoming chromosomes. The microtubules created in the S phase help pull these chromosomes apart, rearranging the interior of the cell. To show this, the Chrome-Zombies have lost their toes and ask “where’s my-toes?”
Story: The Chrome-Zombie has graduated college! This means that it now has the knowledge it needs to go out into the world and become two individual adults. The conjoined twins notice that their shared body is going through some changes as they approach this milestone…their toes are no longer at the end of their feet! “Where’s my-toes?” they ask.
6. Zoom: The sword cutting the Siamese twins in half.
Hot Spot: S-Cyber-Knife - Cytokinesis
Learning: The cell has passed through mitosis and is now ready to divide. This phase is called cytokinesis. The cell’s cytoplasm splits in two, creating two new cells. Cytokinesis is different in plant and animals cells, but it always results in two identical cells. Here, a robot is helping the Siamese Chrome-Zombies divide by cutting them in half with its S-Cyber-Knife, which represents cytokinesis.
Story: Craig and his twin are a little worried about their dysfunctioning Siamese Chrome-Zombie double body. They decide that it’s time to split in half and live life on their own. In order for this to happen, they need a little help from their robot friend and its S-Cyber-Knife. The knife slices down the middle of the zombies’ body, not separating Craig from his brother but instead creating two brand new child zombies. Turns out you can’t be all work or all play after all, and the young zombies now need to start their education all over with a balance of work and play. It’s back to Chrome-Zombie Kindergarten for them!