10 Maret 2026

Summary

This lesson explores the M phase of the cell cycle, focusing on mitosis and cytokinesis. It reviews interphase and explains that M phase involves nuclear division (mitosis) and cytoplasmic division (cytokinesis). Mitosis is detailed in four stages: prophase, where chromatin condenses and spindle fibers form; metaphase, with chromosomes aligned at the cell's equator; anaphase, where sister chromatids separate and move to opposite poles; and telophase, when nuclear membranes reform and chromosomes decondense. Cytokinesis completes cell division, creating two identical daughter cells. Differences in animal and plant cell cytokinesis are highlighted, emphasizing the M phase’s role in producing genetically identical cells.

Takeaways

• 🧬 The M phase is the fourth and final phase of the cell cycle, where cell division occurs.
• 🔬 Interphase consists of G1, S, and G2 phases, and prepares the cell for division.
• 🧪 Mitosis is the division of the nucleus, while cytokinesis is the division of the cytoplasm.
• 📏 Mitosis has four phases: prophase, metaphase, anaphase, and telophase.
• 🌀 During prophase, chromatin condenses into chromosomes, spindle fibers form, and the nuclear membrane and nucleolus disappear.
• 📐 In metaphase, spindle fibers align chromosomes along the cell's equator, ensuring sister chromatids are positioned on opposite sides.
• ✂️ During anaphase, spindle fibers separate sister chromatids at the centromere, pulling them toward opposite poles of the cell.
• 🏁 Telophase involves the reformation of the nuclear membrane, the nucleolus becomes visible, and chromosomes decondense back into chromatin.
• 🧩 Cytokinesis divides the cytoplasm, forming two identical daughter cells; in animal cells, the membrane pinches inward, while in plant cells a cell plate forms.
• ✅ The M phase ensures that two daughter cells are genetically identical to each other and to the original parent cell.

Q & A

What is the M phase of the cell cycle?

The M phase is the fourth and final phase of the cell cycle during which cell division occurs, including both mitosis (division of the nucleus) and cytokinesis (division of the cytoplasm).

What are the two main processes that occur during the M phase?

The two main processes are mitosis, which divides the nucleus, and cytokinesis, which divides the cytoplasm to produce two daughter cells.

What are the four phases of mitosis, and what is the primary event in each?

The four phases are: Prophase – chromatin condenses into chromosomes and the nuclear membrane disappears; Metaphase – chromosomes align along the cell equator; Anaphase – sister chromatids separate and move to opposite poles; Telophase – nuclear membranes reform around chromosomes, which decondense into chromatin.

What is the difference between a centromere and a centriole?

A centromere is the region of a chromosome where sister chromatids are joined, while centrioles are structures at the poles of the cell that help organize spindle fibers during mitosis.

What role do spindle fibers play during mitosis?

Spindle fibers attach to centromeres of chromosomes and help align them during metaphase and separate sister chromatids during anaphase.

How does cytokinesis differ between animal and plant cells?

In animal cells, the cell membrane pinches inward to divide the cytoplasm. In plant cells, a cell plate forms at the equator and eventually develops into a new cell wall, separating the daughter cells.

During which phase of mitosis do chromosomes first become visible as individual structures?

Chromosomes first become visible as individual structures during prophase when chromatin condenses into tightly coiled sister chromatids.

What happens to the nucleolus and nuclear membrane during mitosis?

The nucleolus and nuclear membrane disappear during prophase and reform during telophase after chromosome separation is complete.

What is the shape of chromosomes as they move toward the poles during anaphase, and why?

They form a V-shape because spindle fibers pull the chromatids through the gel-like cytoplasm toward the centrioles at opposite poles.

Why are the two daughter cells produced after M phase identical to each other and to the original cell?

Because mitosis ensures that each daughter cell receives an exact copy of the original cell’s DNA, and cytokinesis equally divides the cytoplasm and organelles, resulting in two genetically identical cells.

What happens to chromosomes during telophase?

During telophase, chromosomes decondense back into chromatin, and the nuclear membrane and nucleolus reform around each set of chromosomes.

Why is it important not to confuse centrioles with centromeres?

Centrioles are located at the poles and help organize spindle fibers, while centromeres are part of the chromosome that holds sister chromatids together; confusing them could lead to misunderstanding the mechanics of chromosome separation.