K325 / 2027

Lesson 1 of 12 / Reproduction

Mitosis makes matching cells

How can one organism grow or make offspring without combining two gametes?

In this lesson: Explain asexual reproduction and the role of mitosis in growth, repair and reproduction.

About 5 min

The key ideaMitosis maintains chromosome number and produces genetically identical cells; it supports growth, repair and asexual reproduction.

Mitosis preserves four chromosomes in each daughter cellDiploid parent: 2n = 4Predict the number in each new cell
The model species has two homologous pairs: one long pair and one short pair.

Bars stand for chromosomes; DNA copying and division stages are omitted to focus on sets. The meiosis model isolates assortment without crossing over, so some products shown match. It is not a diagram of four equally developed human egg cells.

Explanation

Asexual reproduction produces genetically identical offspring from one parent, without fusion of gametes. For example, a new strawberry plant can grow from a runner connected to the parent. Such offspring are often called clones.

Mitosis is nuclear division that gives genetically identical daughter nuclei with the same chromosome number as the parent nucleus. Division of the cell usually follows, producing two daughter cells. DNA is copied before the division so each receives a complete matching set.

Mitosis enables growth by increasing cell number. It supports repair by replacing damaged or worn-out cells, and it supplies the new cells needed in many forms of asexual reproduction.

A new cell is not automatically a new organism. Mitosis in human skin repairs one organism; mitosis involved in a plant runner can help produce an independent offspring. The role depends on the context.

Genetically identical is the expected result when copying is accurate; mutations can introduce differences. Identical genes also do not guarantee identical appearance if the offspring grow in different environments.

Step by step
  1. 1

    Identify the outcome

    Is the organism growing, replacing cells or producing a new organism?

  2. 2

    Track the chromosome number

    Mitosis gives each daughter nucleus the same number as the parent nucleus.

  3. 3

    Check for gamete fusion

    Asexual reproduction does not involve fusion of male and female gamete nuclei.

Worked example

Repairing skin

A skin cell with 46 chromosomes divides by mitosis. State the expected chromosome number in each daughter cell and explain the benefit.

One way to explain it

Each daughter cell has 46 chromosomes and the same genetic information as the original cell, assuming accurate copying. This supplies matching cells to replace damaged skin and repair the tissue.

Why this answer works
  • The number is maintained in each cell, not shared as 23 each.
  • Use repair rather than calling every division reproduction of a person.
Is this true? "Two daughter cells must each receive half the normal chromosome number during mitosis."

DNA is copied before division. Each daughter cell receives a full matching set, so chromosome number is maintained.

Try a question

Which describes a plant producing a new plant from a runner?
You can return to this lesson any time.