Question

Eukaryotic chromosomes metabolically are most active during which phase?

• A. Prophase
• B. Metaphase
• C. Interphase
• D. Telophase

Hint:

To perform transcription and replication, DNA must be uncoiled.
Uncoiled DNA (euchromatin) is found only during Interphase, making it the most metabolically active phase.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The cell cycle is divided into Interphase (growth and replication) and M-phase (mitosis or meiosis).
Chromosomes change their structural state dramatically to match the functional needs of the cell.
During division, DNA must be packaged tightly to prevent damage during movement.
During growth and synthesis, DNA must be physically accessible to enzymes.

Step 2: Detailed Explanation:
Let us evaluate the state of chromosomes in the cell cycle phases.
1. During M-phase (Prophase, Metaphase, Anaphase, Telophase), chromosomes undergo intensive condensation.
Highly condensed chromosomes are transcriptionally inactive because the tightly packed structure prevents RNA polymerase and transcription factors from accessing the gene sequences.
2. During Interphase (G1, S, and G2 phases), chromosomes are in a decondensed, open chromatin state (euchromatin).
This loose structure allows the gene expression machinery to transcribe DNA into mRNA.
Furthermore, DNA replication occurs during the S-phase of Interphase, which requires high metabolic energy and enzyme activity.
Thus, the chromosomes are at their maximum level of metabolic and transcriptional activity during Interphase.

Step 3: Final Answer:
Eukaryotic chromosomes are metabolically most active during Interphase.