Mitosis Microscope Practical

Overview

In this practical, students examine prepared onion root-tip cells to identify the stages of mitosis and collect class data. They apply microscope skills, calculate the proportion of cells in each stage and explain how cell division produces genetically similar daughter cells while maintaining chromosome number.

Learning intentions

Students will:

• Identify interphase, prophase, metaphase, anaphase and telophase/cytokinesis in prepared root-tip cells.
• Use a light microscope safely and systematically to locate, focus and observe cells.
• Record tally data and calculate the proportion of cells in each mitotic stage.
• Explain how chromosome number is maintained during mitosis.
• Evaluate limitations of using prepared slides to estimate the frequency of cell-cycle stages.

Success criteria

• I can identify mitotic stages using visible features such as chromosome arrangement and separation.
• I can use a microscope safely, beginning on low power and focusing accurately.
• I can record observations in a clear tally table and calculate proportions correctly.
• I can explain why mitosis produces daughter cells with the same chromosome number as the parent cell.
• I can describe at least one limitation of my sample or method.

Curriculum links

• Cells as the basis of life: cell structures and functions, biochemical processes and cell division.
• Students explain how cell structures enable biological processes needed for life, including the role of chromosomes and the nucleus during cell division.
• Students explain how cells contribute to complex multicellular organisms through growth, repair and replacement of cells.
• Students identify components of living things and their functions, including the nucleus and genetic material.

Lesson structure (60 minutes)

1. 0–5 min · Hook and retrieval. Teacher displays a root-tip micrograph and asks, “Why might cells near a root tip show different chromosome arrangements?” using the opening micrograph and retrieval questions. Students individually identify any visible patterns, then share one idea and recall the purpose of cell division.

2. 5–15 min · Explicit teaching. Teacher uses the mitosis teaching slides to review the cell cycle and model the visual features of interphase, prophase, metaphase, anaphase and telophase/cytokinesis. Students annotate the corresponding diagrams on the mitosis practical recording sheet and answer: “At which stage are chromosomes aligned?” and “When do sister chromatids separate?”

3. 15–22 min · Microscope demonstration and safety. Teacher demonstrates carrying, setting up and focusing a microscope, including low-power scanning, careful use of the coarse and fine adjustment knobs, and safe slide handling. Students watch for the correct sequence, repeat the sequence verbally with a partner and complete the safety check on the mitosis practical recording sheet.

4. 22–42 min · Practical observation. Teacher places students in groups of three, assigns rotating roles—microscope operator, recorder and equipment manager—and circulates to question identifications. Students examine prepared root-tip slides, locate a suitable region and tally at least 50 cells by stage on the mitosis practical recording sheet, recording uncertain cells separately rather than guessing.

5. 42–52 min · Data analysis. Teacher pauses the practical and models one calculation from the class data shown in the data-analysis and calculation slides. Students total their tallies, calculate the proportion and percentage of cells in each stage, then compare results with another group and identify one similarity and one difference.

6. 52–57 min · Evaluation and explanation. Teacher leads a brief discussion using the evaluation discussion slides: “Does the proportion of cells in a stage prove how long that stage lasts?” Students write a short explanation linking the nucleus, chromosomes, DNA replication and equal distribution of genetic material to maintenance of chromosome number. They also describe two limitations, such as sample size, field of view, slide preparation or difficulty distinguishing stages.

7. 57–60 min · Plenary and exit check. Teacher displays the final questions on the plenary and exit-ticket slide. Students submit answers to: “How does mitosis maintain chromosome number?” and “Which stage was easiest or hardest to identify, and why?” Students return microscopes, slides and worksheets according to laboratory procedures.

Resources

• Prepared onion root-tip mitosis slides
• Light microscopes, one per group where possible
• Microscope slide boxes and lens paper
• the mitosis microscope practical deck
• the mitosis practical recording sheet
• Safety glasses and laboratory coats, as required by school procedures
• Whiteboard or display for class data
• Calculators
• Paper towel and disinfectant for equipment benches

Assessment

• During teaching, question students about the visual evidence used to identify each stage and check their microscope setup before observation begins.
• Review group tally tables for systematic counting, appropriate stage identification and separation of uncertain observations.
• Use the exit responses to assess whether students can explain chromosome-number maintenance and evaluate limitations of prepared-slide evidence.

Differentiation

• Provide a labelled stage-reference diagram, a visual checklist for microscope focusing and sentence starters such as “Chromosome number is maintained because…” for students requiring support.
• Allow students to work with a peer expert and record observations using a prepared table; provide enlarged micrographs or a digital microscope image if visual access is difficult.
• Support EAL/D students with a small illustrated glossary for chromosome, chromatid, nucleus, aligned, separated and daughter cell, while modelling each term orally.
• Extend capable students by asking them to use the class proportions to infer which stages occupy more time in the cell cycle, then explain why this inference is tentative and affected by sampling limitations.