Cells and Cell Division
Grade 7 · Science · Study Guide
Explore how living cells grow, duplicate, and pass on genetic information through mitosis.
Every living thing on Earth is made of cells — the smallest unit of life. Some organisms, like bacteria, are just one cell. You are made of about 37 trillion cells, each doing a specific job. Cells come in two major types: prokaryotic cells (no nucleus, like bacteria) and eukaryotic cells (have a nucleus, like your own cells). The nucleus is the control center, holding DNA with instructions for everything the cell does.
Cells don't live forever. They grow, do their jobs, and eventually divide or die. When your skin heals after a cut, that is new cells being made. The process of a cell splitting into two identical daughter cells is called mitosis. Before a cell can divide, it must copy all of its DNA so each new cell gets a complete set of instructions. This copying phase is called DNA replication.
Mitosis has four main stages: prophase (DNA condenses into visible chromosomes), metaphase (chromosomes line up in the middle), anaphase (chromosomes are pulled to opposite ends), and telophase (two new nuclei form). After mitosis, the cell splits in a process called cytokinesis, producing two genetically identical cells. This is how your body grows and repairs itself.
Not all cell division is for growth and repair. Some specialized cell division — called meiosis — makes reproductive cells (sperm and eggs) with half the normal number of chromosomes. When sperm and egg combine, the resulting cell has the full count again. Understanding cell division helps scientists fight cancer, which is essentially uncontrolled cell division gone wrong.
| Stage | What Happens |
|---|---|
| Prophase | DNA coils into visible chromosomes; nuclear envelope breaks down |
| Metaphase | Chromosomes line up along the cell's middle (equator) |
| Anaphase | Sister chromatids are pulled apart to opposite poles |
| Telophase | Nuclear envelopes re-form around each set of chromosomes |
| Cytokinesis | Cytoplasm divides; two identical daughter cells are produced |
Key terms
- Cell
- The basic unit of structure and function in all living organisms.
- Nucleus
- The membrane-bound organelle that contains the cell's DNA and controls its activities.
- Mitosis
- Cell division that produces two genetically identical daughter cells for growth and repair.
- Chromosomes
- Tightly coiled structures made of DNA that carry genetic information.
- Cytokinesis
- The physical splitting of one cell into two after the nucleus has divided.
- DNA replication
- The process of copying DNA before cell division so each daughter cell gets a complete set.
Flashcards
- Cell membrane
- Flexible outer boundary that controls what enters and exits the cell.
- Mitochondria
- The 'powerhouse' organelle that produces ATP energy for the cell.
- Prophase
- First stage of mitosis when chromosomes become visible.
- Metaphase
- Stage when chromosomes align along the cell's equator.
- Anaphase
- Stage when sister chromatids are pulled to opposite poles of the cell.
- Telophase
- Final stage of mitosis when two new nuclei form.
Practice questions
What is the main purpose of mitosis in the human body?
- To produce sperm and egg cells
- To allow growth and repair of tissues
- To create energy for the cell
- To destroy old proteins
Show answer
Answer: To allow growth and repair of tissues
Mitosis produces identical cells for growth, repair, and replacement of worn-out cells — not for reproduction.
Prokaryotic cells have a membrane-bound nucleus.
Show answer
Answer: False
Prokaryotic cells (like bacteria) have no membrane-bound nucleus; their DNA floats freely in the cytoplasm.
During which stage of mitosis do chromosomes line up in the middle of the cell?
- Prophase
- Anaphase
- Metaphase
- Telophase
Show answer
Answer: Metaphase
Metaphase is the stage where chromosomes align at the cell's equator, making them easy to count and study.
The physical splitting of the cytoplasm into two cells after nuclear division is called ___.
Show answer
Answer: cytokinesis
Cytokinesis is the physical division of the cell body that follows nuclear division, completing the production of two daughter cells.
The two daughter cells produced by mitosis are genetically identical to the parent cell.
Show answer
Answer: True
Because DNA is replicated before mitosis begins, both daughter cells receive an identical copy of the genetic information.
Fun facts
- Your body produces about 25 million new cells every single second.
- The largest cell in the human body is the egg cell — it is just barely visible to the naked eye.
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