Mitosis & the Cell Cycle — Drills · Grade 10 Science

Chapter: Cell Division, Reproduction & Development

What these drills covers

By the end of Mitosis & the Cell Cycle you should be able to:

6 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: cell cycle, interphase, mitosis, sister chromatids, cytokinesis, daughter cell, centromere, G₁, S and G₂.

Problem 1

DNA is replicated during which part of the cell cycle?
  1. Prophase
  2. The S phase of interphase
  3. Anaphase
  4. Cytokinesis
Answer and explanation

The S phase of interphase

Replication occurs in the S phase of interphase, before mitosis begins, so each chromosome enters mitosis already duplicated.

Problem 2

The function of mitosis is to produce
  1. four haploid cells
  2. two cells with the same chromosome number as the parent
  3. gametes for reproduction
  4. cells with half the DNA of the parent
Answer and explanation

two cells with the same chromosome number as the parent

Mitosis divides duplicated chromosomes equally, giving two cells with the parent's chromosome number. Meiosis produces haploid gametes.

Problem 3

A cell with 46 chromosomes completes mitosis. How many chromosomes does each daughter cell contain?
Answer and explanation

46

Each daughter receives one copy of every replicated chromosome, so the number is maintained at 46.

Problem 4

In a field of 200 root-tip cells, 30 are in mitosis. If the full cycle takes 20 hours, estimate the duration of mitosis in hours.
Answer and explanation

3 hours

30/200 = 0.15 of the cycle, and 0.15 × 20 = 3 hours. The estimate assumes cells are dividing asynchronously and that the sample is representative.

Problem 5

Cell-cycle checkpoints exist to
  1. speed up division in all cells
  2. verify that conditions and DNA are suitable before the cycle proceeds
  3. remove chromosomes
  4. prevent interphase
Answer and explanation

verify that conditions and DNA are suitable before the cycle proceeds

Checkpoints halt the cycle when DNA is damaged, replication is incomplete, or chromosomes are not properly attached, so faults are repaired rather than propagated.

Problem 6

Explain why uncontrolled cell division is dangerous to an organism even though cell division itself is normal and necessary.
Answer and explanation

Division is required for growth, repair, and replacement, but it is normally regulated so that cells divide only when needed and only when checkpoints are satisfied. When that regulation fails, cells divide regardless of the organism's needs or of DNA damage, forming a mass that consumes resources, displaces or invades surrounding tissue, and can spread. The problem is the loss of control over timing and quality, not division as such.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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