Cell cycle - microbiology, biology, physiology

Summary

The cell cycle is the process by which somatic cells grow and divide. It consists of two main phases: interphase and mitosis. Interphase is divided into G1, S, and G2 phases, where the cell grows, replicates DNA, and prepares for division. In mitosis, the cell divides its DNA and separates into two daughter cells through stages including prophase, metaphase, anaphase, telophase, and cytokinesis. Some cells enter a non-dividing state called the G0 phase. This cycle ensures that cells divide accurately and function properly, playing a crucial role in growth, repair, and maintenance of tissues.

Takeaways

• 😀 The cell cycle refers to the process somatic cells go through from formation to division into two identical daughter cells.
• 😀 The cell cycle consists of two main phases: Interphase (preparation) and Mitosis (division).
• 😀 Interphase includes three sub-phases: G1 (growth), S (DNA replication), and G2 (growth and preparation for division).
• 😀 During G1, the cell grows, performs regular functions, and checks for DNA damage at the G1 checkpoint.
• 😀 In the S phase, DNA is replicated, ensuring identical genetic material is passed to both daughter cells.
• 😀 The G2 phase involves further growth and the duplication of organelles before entering mitosis.
• 😀 Mitosis consists of four subphases: Prophase, Metaphase, Anaphase, and Telophase, followed by Cytokinesis.
• 😀 During Prophase, the nuclear membrane disintegrates, and chromosomes condense, becoming visible.
• 😀 In Metaphase, chromosomes line up at the cell's equator, and spindle fibers attach to the chromosomes.
• 😀 Anaphase involves the separation of sister chromatids, which are pulled toward opposite poles of the cell.
• 😀 Telophase forms two new nuclear membranes around the separated chromatids, and Cytokinesis divides the cell into two distinct daughter cells.

Q & A

What is the cell cycle and what does it include?

The cell cycle refers to the series of events that somatic cells go through from the moment they are formed until they divide into two identical daughter cells. It includes both the preparation phase (interphase) and the division phase (mitosis).

How long does the cell cycle take?

The length of the cell cycle varies depending on the type of cell. For rapidly dividing cells, like skin cells, the cycle takes less than a day. For slower dividing cells, like liver cells, the cycle can last years.

What are the two main phases of the cell cycle?

The two main phases of the cell cycle are interphase and mitosis. Interphase is the phase of preparation, and mitosis is the phase of cell division.

What happens during the interphase?

During interphase, the cell grows, carries out its regular functions, and replicates its DNA in preparation for mitosis. It can be broken down into three sub-phases: G1, S, and G2.

What is the G1 phase of the cell cycle?

The G1 phase (Gap 1) is the longest phase of the cell cycle, where the cell grows and performs regular cellular functions, such as synthesizing proteins and producing energy.

What is the significance of the G1 checkpoint?

At the G1 checkpoint, the cell checks whether its DNA is damaged and if the correct proteins have been synthesized. If issues are found, the cell may enter a non-dividing state called the G0 phase or undergo apoptosis (self-destruction).

What happens during the S phase?

During the S phase (synthesis), DNA is replicated, ensuring that each daughter cell will receive identical copies of the genetic material. The amount of DNA doubles, but the number of chromosomes remains the same.

What occurs during the G2 phase?

During the G2 phase (Gap 2), the cell continues to grow and prepares for mitosis by duplicating its organelles. It must pass the final G2 checkpoint before entering mitosis.

What is mitosis and what are its stages?

Mitosis is the process where the cell divides into two daughter cells. It involves separating replicated DNA into two nuclei (kinesis) and dividing the cell membrane to form two separate cells (cytokinesis). Mitosis consists of four stages: prophase, metaphase, anaphase, and telophase.

What is the G0 phase and what types of cells enter this phase?

The G0 phase is a non-dividing state where cells are alive but not actively preparing to divide. Some cells, like neurons, spend their entire life in G0, while others, like hepatocytes (liver cells), enter G0 temporarily before dividing again if needed.