|Cell cycle||The series of growth and development steps a cell undergoes between its formation and reproduction|
|Interphase||Phase of the cell cycle where the cell grows and makes a copy of its DNA|
|Mitosis||Phase of the cell cycle where the cell separates its DNA into two sets and divides, forming two new cells|
|Cancer||A disease of uncontrolled cell growth|
The cell cycle
In eukaryotic cells, the cell cycle is divided into two major phases: interphase and mitosis (or the mitotic (M) phase).
Interphase is the longest part of the cell cycle. This is when the cell grows and copies its DNA before moving into mitosis. During mitosis, chromosomes will align, separate, and move into new daughter cells.
The prefix inter- means between, so interphase takes place between one mitotic (M) phase and the next.
Interphase consists of three steps:
phase: first gap phase; the cell grows larger and organelles are copied
- S phase: synthesis phase; the cell synthesizes a complete copy of the DNA in its nucleus
phase: second gap phase; the cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis
Cells that are meant to divide will complete G
and enter mitosis. Other types of cells that divide slowly or not at all may exit the G phase and enter a non-dividing state called G . Some cells remain here indefinitely, while others may re-enter division under the right conditions.
Mitosis (the M phase)
The process of mitosis, or cell division, is also known as the M phase. This is where the cell divides its previously-copied DNA and cytoplasm to make two new, identical daughter cells.
Mitosis consists of four basic phases: prophase, metaphase, anaphase, and telophase.
Stages of mitosis
Cancer and cell cycle regulation
The cell cycle is usually regulated by checkpoints. These are the factors that a cell considers when deciding whether or not to move forward through the cell cycle, and include both external cues (like molecular signals) and internal cues (like DNA damage).
Cancer is a term that describes many different diseases caused by the same problem: uncontrolled cell growth.
Most cancers occur due to a series of mutations that make them divide more quickly, bypass checkpoints during cell division, and avoid apoptosis (programmed cell death).
Generally, mutations of two types of cell cycle regulators can promote the development of cancer:
- Positive regulators, which normally promote cell growth, may become hyperactivated (oncogenic).
- Negative regulators (tumor suppressors), which prevent the formation of tumors, may become inactivated.
Często spotykane błędy i nieporozumienia
- Interphase is not part of mitosis. Although we often talk about interphase and mitosis together, interphase is technically not part of mitosis. However, both processes are part of the larger cell cycle, where interphase consists of the G
, S, and G stages of the cell cycle.
- DNA replication occurs during interphase, not prophase. A common misconception is that DNA copies itself during prophase, but this is not true. In prophase, the DNA has already been copied while the cell was in interphase.
- The chromosome number is the same in the daughter cells as it was in the parent cell. Because DNA is duplicated during interphase before the cell undergoes mitosis, the amount of DNA in the original parent cell and the daughter cells are exactly the same.
- Both genetics, as well as external factors, can play a role in the development of cancer. Many types of cancer have a genetic component, so inheriting certain genes may make someone more likely to get these types of cancer. However, having these genes does not necessarily mean that cancer will develop, as factors such as lifestyle and environment also play a part.