Explain how a diploid skin cell produces two genetically identical daughter cells during the cell cycle.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Skin cells are constantly dividing to replace cells lost from the surface of the body. Each new cell must contain a full set of chromosomes identical to the parent cell.
Model answer (5 marks)
During interphase the cell undergoes S phase, where the DNA is replicated so each chromosome becomes a pair of identical sister chromatids. In prophase the chromatin condenses into visible chromosomes and the nuclear envelope breaks down. At metaphase the chromosomes line up at the metaphase plate (cell equator) with the help of the mitotic spindle. During anaphase the sister chromatids are pulled apart by the spindle fibres to opposite poles of the cell. Finally, cytokinesis divides the cytoplasm and the cell membrane, producing two new daughter cells. Each daughter cell is diploid, containing a full set of chromosomes, and is genetically identical to the parent skin cell.
Examiner tips
- Mention S phase DNA replication first
- Show the sequence of mitotic stages in order
- Include cytokinesis as the final step
- State that the daughter cells are diploid and genetically identical
Common mistakes
- Confusing meiosis with mitosis
- Omitting the S phase or cytokinesis
- Failing to state that the daughter cells are diploid and identical
Mark scheme (5 marks)
- During interphase, DNA replication occurs so each chromosome is copied / the cell's DNA is replicated
- During metaphase, chromosomes align at the cell equator
- During anaphase, chromatids are pulled to opposite poles of the cell by spindle fibres
- Cytokinesis divides the cytoplasm to produce two new daughter cells
- Each daughter cell is diploid / contains a full set of chromosomes / is genetically identical to the parent skin cell
Key terms in this question
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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