Q1. What are phase I, II, III, IV, and V in this diagram?

Background

Topic: Cell Cycle and DNA Replication

This question tests your understanding of the stages of the cell cycle, particularly how the amount of DNA in the nucleus changes during each phase. The diagram shows the relative amount of DNA in a cell nucleus over two cycles, which is key to identifying the phases of interphase and mitosis/meiosis.

Key Terms and Concepts:

• Interphase: The phase where the cell grows and DNA is replicated (includes G1, S, and G2 phases).

• Mitosis/Meiosis: The process of cell division, where the nucleus divides and DNA is distributed to daughter cells.

• G1 Phase: Cell grows, DNA content is unchanged.

• S Phase: DNA synthesis/replication occurs, doubling the DNA content.

• G2 Phase: Cell prepares for division, DNA content remains doubled.

• M Phase: Mitosis or meiosis, DNA is divided between daughter cells, DNA content returns to original.

Step-by-Step Guidance

1. Observe the graph: The y-axis represents the amount of DNA in the nucleus, and the x-axis shows progression through two cell cycles.

2. Identify the regions where the DNA amount is constant (flat lines) and where it increases or decreases (sloped lines).

3. Recall that DNA replication (S phase) is the only time DNA amount increases, while mitosis/meiosis (M phase) is when DNA amount decreases as cells divide.

4. Match each labeled phase (I, II, III, IV, V) to the corresponding cell cycle stage based on whether DNA is being synthesized, remains constant, or is being divided.

5. For each phase, consider: Is the cell preparing for division, replicating DNA, or actually dividing? Use the changes in DNA amount as your guide.

Try solving on your own before revealing the answer!