Mitosis and Meiosis

• newEditor
• Biologie
• Middelbare school
• havo
• Leerjaar 3

Onderwerp: Mitosis

Lesdoel: I can name the phases of Mitosis and explain what happens during each phase.

Starttaak:

• Join the LessonUp

• In your zuidschrift: Why do cells need to divide (multiply)? Write 3 full sentences to explain.

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How Cells Divide

Two ways cells divide

• Mitosis makes new cells for growth and repair.

• Meiosis happens when sex cells are formed.

• In mitosis, the phases are prophase → metaphase → anaphase → telophase.

• In meiosis, the same phase names are used twice: I and II.

Read the goal aloud. Explain that the Roman numerals show the first and second division. Begin with mitosis; meiosis comes later.

Why mitosis matters

After a graze, the body needs new skin cells. Mitosis produces these new cells, so tissue can grow and repair itself.

Use the graze as an everyday example. Link repair to growth: both need new cells made by mitosis.

DNA, chromosomes and chromatids

• DNA contains hereditary information.

• A chromosome is made of DNA and proteins.

• Before division, the DNA is copied.

• A copied chromosome has two sister chromatids.

• They are attached at the centromere.

Draw one rod first, then one X. Point to the two halves and say they are two copies of the same chromosome.

Before mitosis begins

• During interphase, the cell grows and copies its DNA.

• Then mitosis begins: the copied chromosomes are divided between two new nuclei.

• During cytokinesis, the cytoplasm is divided.

• Result: two daughter cells with the same number of chromosomes as the original cell.

Emphasise that DNA is copied before mitosis, not during prophase. No need to teach G1, S and G2 separately here.

In biology, what does an X-shaped chromosome show?

A

One copied chromosome

B

Two different chromosomes

C

A cell nucleus

D

One DNA base pair

Before mitosis

During interphase, the cell grows and copies its DNA. Then mitosis divides the copied chromosomes between two new nuclei. During cytokinesis, the cytoplasm is divided, forming two daughter cells.

interphase

mitosis

cytokinesis

prophase

metaphase

centromere

chromatid

If students struggle, remind them of the sequence: preparation first, nuclear division next, cytoplasm division last.

Mitosis: four key features

1. Prophase: chromosomes become compact and visible; the spindle forms and the nuclear membrane disappears.

2. Metaphase: copied chromosomes line up separately in the middle.

3. Anaphase: sister chromatids separate and move to opposite sides.

4. Telophase: new nuclear membranes form around both groups of chromosomes.

Model the recognition aloud: visible — middle — separate — new nuclei. Keep telophase distinct from cytokinesis.

Recognising prophase

• DNA has already been copied.

• Chromosomes become compact and visible.

• The spindle starts to form.

• The nuclear membrane disappears.

Point out why this is not metaphase yet: the chromosomes are not lined up in the middle.

Recognising metaphase

• Copied chromosomes lie in one row in the middle.

• The sister chromatids are still attached.

• This is the stage before separation.

Use the word 'middle' as the key evidence.

Recognising anaphase

• Sister chromatids separate.

• They move to opposite sides of the cell.

• After separation, each chromatid is counted as an individual chromosome.

Recovery sentence: anaphase means the copies move apart. Ask what exactly is separating.

Recognising telophase

• The chromosomes have reached both sides.

• A new nuclear membrane forms around each group.

• Two new nuclei appear.

• Cytokinesis is the division of the cytoplasm, not the nucleus.

Highlight the difference between nuclear division and cytoplasm division.

Mitosis in order

Prophase - chromosomes become visible

Metaphase - chromosomes line up in the middle

Anaphase - sister chromatids separate

Telophase - new nuclei form

Use the memory anchor P → M → A → T. If needed, prompt with: visible, middle, apart, new nuclei.

Which phase shows chromosomes in one row in the middle?

A

Anaphase

B

Prophase

C

Metaphase

D

Telophase

Distractors match nearby phases students often confuse. The key evidence word is middle.

Mitosis in order

In prophase, chromosomes become visible. In metaphase, they line up in the middle. In anaphase, sister chromatids separate. In telophase, new nuclei form.

prophase

metaphase

anaphase

telophase

interphase

cytokinesis

centromere

spindle

This anchors both order and recognition points: visible, middle, separate, new nuclei.

Which mitosis phase do you find hardest to recognise? Why?

Expected elements: the four phases in the correct order with one feature each — prophase: visible/compact chromosomes; metaphase: middle; anaphase: chromatids separate; telophase: new nuclei. Accept equivalent wording.

What is one thing you will remember about mitosis?

Reflection only. Invite short personal responses about what they learned best in this lesson.

What part of today's lesson felt hardest?

Reflection only. Useful for checking whether the phase names, chromosome terms or order caused difficulty.

What helped you understand the phases best?

Reflection only. Encourage students to mention a strategy, example or memory anchor such as P-M-A-T or visible-middle-separate-new nuclei.

Glossary

DNA - the molecule that contains hereditary information

chromosome - a structure made of DNA and proteins

chromatid - one half of a copied chromosome

sister chromatids - two identical chromatids joined together

centromere - the region where sister chromatids are attached

interphase - the stage when the cell grows and copies its DNA

cytokinesis - division of the cytoplasm into two cells

Glossary

mitosis - cell division for growth and repair

meiosis - cell division that forms sex cells

prophase - phase when chromosomes become visible

metaphase - phase when chromosomes line up in the middle

anaphase - phase when sister chromatids separate

telophase - phase when new nuclei form

spindle - structure that moves chromosomes during division