BIO 101 LAB

Overview of Mitosis

Mitosis is a type of cell division used to produce body cells, specifically designed to make identical cells.
The primary goal of mitosis is to replace worn or damaged cells with identical cells, ensuring that the same type of cells is generated (e.g., skin cells replacing skin cells).
Mitosis is critical for growth and repair in the body.

Cells do not divide continuously; uncontrolled cell division can lead to cancer, characterized by uncontrolled growth.
The cell's life cycle consists of phases, primarily divided into Interphase and mitosis (also referred to as the mitotic phase).

Interphase is the longest phase in the cell cycle, where the cell grows, replicates DNA, and carries out daily functions.
During interphase, the following stages occur:
- G1 (First Gap): Phase where the cell grows and synthesizes proteins needed for DNA replication.
- S (Synthesis): DNA synthesis occurs; the cell duplicates its DNA to ensure that each new cell gets a complete set of chromosomes.
- G2 (Second Gap): Another growth phase where the cell prepares for mitosis, ensuring all DNA and organelles are appropriately replicated.

DNA is organized into structures called chromosomes, which consist of DNA and protein.
Humans have 46 chromosomes within each body cell nucleus. The noun form of nucleus is nuclei (not nucleuses).
Chromosomes condense and become visible during cell division, particularly in prophase, making it easier for the cell to separate the genetic material.

Mitosis is often summarized with the acronym PMAT:
- P - Prophase:
- The nucleus is still present.
- Chromosomes become visible and condense.
- The mitotic spindle starts to form.
- M - Metaphase:
- The nucleus has broken down.
- Chromosomes line up in the middle of the cell, ready for segregation.
- A - Anaphase:
- Chromosomes (sister chromatids) are pulled apart and move toward opposite poles of the cell.
- They are moved by spindle fibers, which are essential for the movement of chromosomes.
- T - Telophase:
- Chromosomes arrive at the poles and start to relax back into chromatin.
- New nuclear envelopes form around each set of chromosomes, creating two separate nuclei.
After mitosis is completed, cytokinesis occurs, where the cell membrane pinches inwards or a cell plate is formed (in plant cells) to complete the division into two daughter cells.

Cytokinesis is the final separation of the cytoplasm into two cells.
- In animal cells, this often involves the formation of a cleavage furrow that pinches the cell apart.
- In plant cells, a cell plate forms that will eventually develop into a new cell wall.
New cells created through mitosis are referred to as daughter cells, maintaining the same chromosome number as the parent cell.

Understanding mitosis is crucial for comprehending growth, development, and the repair processes in living organisms.
Mitosis is also a significant area of study in cancer research due to the connection between uncontrolled cell division and cancer development.

The cell cycle takes approximately 24 hours to complete from one cell to two cells.
Examples of cells requiring significant mitosis include red blood cells, skin cells (replaced every four weeks), and cells involved in local tissue repair.
Certain cells, such as neurons, have limited regenerative capabilities, but mitosis plays a key role in repair for many other cell types.
During the preparation for mitosis, sister chromatids (identical copies of chromosomes) are formed. Each contains tightly coiled DNA with associated histone proteins.
Mitosis is observable under a microscope in prepared slides, such as onion root cells, where various phases of mitosis can be identified.

Time-lapse videos can illustrate the rapid progression of mitosis in cells, demonstrating how quickly processes occur in a real biological context.