Decoding The Cell Cycle
Imagine an organism growing from a single cell into billions of cells as it ages. This growth is made possible through a process called cell division, where cells replicate and repair themselves. In this blog post, we will explore the cell cycle, which is a series of steps that eukaryotic cells go through to produce more cells and repair damaged ones.
What is the Cell Cycle?
The cell cycle consists of two main phases: interphase and mitosis (M Phase). Interphase is the longest phase, and it involves various steps and checkpoints to ensure the cells produce identical daughter cells with the same genetic information. Mitosis, on the other hand, is the phase where cell division actually takes place. In this post, we will provide a general overview of the cell cycle, focusing specifically on interphase. Subsequent posts will focus on the cell cycle checkpoints and mitosis.
Purpose of The Cell Cycle
The cell cycle occurs in eukaryotic cells, particularly in somatic cells, which are cells that belong to the body. These cells can be found in multicellular organisms like humans. The primary objective of the cell cycle is to create two identical cells. This process serves two purposes: growth and repair.
Growth: Organisms grow by increasing the number of cells through cell division. As humans, we start as a single cell, but as we age, our cells divide and differentiate, leading to the growth and development of our bodies. For this growth to occur, cells need to divide while maintaining the same genetic information stored in DNA. Throughout the cell cycle, a cell must prepare to ensure that the resulting daughter cells have identical genetic information.
Repair: Cells can get damaged or become old over time. Cell division plays a crucial role in replacing lost or damaged cells. In our bodies, cells can specialize to perform specific functions. For example, the cells in our intestines aid in digestion but can also get damaged during the process. Therefore, these cells need to be replaced to maintain proper functioning. Additionally, cells have a limited lifespan and can become worn out after numerous divisions. The cell cycle and cell division help replace old, damaged cells with new ones.
Cell Cycle Overview
The cell cycle can be divided into interphase and mitosis. Interphase is where the cell spends most of its time, preparing for division during mitosis. Let's take a closer look at the phases within interphase:
G1 Phase: This is the initial phase of the cell cycle. During G1, the cell prepares for DNA synthesis by increasing in size and producing more organelles like mitochondria.
S Phase: In the S phase, DNA synthesis occurs. This means that a second copy of DNA is produced, resulting in two copies within the nucleus.
G2 Phase: Following DNA synthesis, the cell continues to grow in the second gap phase (G2). It increases in size, produces additional proteins and organelles to support the growth, and prepares the cell for mitosis.
G1, S, and G2 phases collectively prepare the cell for mitosis, where active cell division occurs. Interphase comprises around 90% of the cell cycle, while mitosis accounts for approximately 10%. However, different cells have varying replication rates and may spend different amounts of time in each phase.
However, not every cell will divide and there are instances where cells are not preparing to divide. When this happens, the cell enters the G0 (G Zero) Phase.
G0 Phase: Sometimes, a cell may not divide. In such cases, the cell exits the cell cycle and enters a resting phase called G0. This can occur when conditions and resources are not favorable for division and growth. Certain mature human nerve cells, for instance, permanently remain in the G0 phase and do not divide. This is why nerve cell damage can lead to severe injuries.
Conclusion
Cell division is a constant process in our bodies and other organisms. This blog post provides a snapshot of cell division and interphase, but the process is incredibly complex. It requires precise coordination of phases, checkpoints, and factors to produce two identical daughter cells. In the upcoming posts of this series, we will explore some of these checkpoints and factors and how they relate to cancer, mitosis, and more!
