Question

Beginning with the \(\mathrm{G}_{1}\) phase of the cell cycle, describe the level of compaction of the eukaryotic chromosome. How does the level of compaction change as the cell progresses through the cell cycle? Why is it necessary to further compact the chromatin during mitosis?

Short answer

Starting with the G1 phase of the cell cycle, chromosomes are less compact. Compaction increases as the cell progresses through the cell cycle, with the highest level of compaction during mitosis. This high level of compaction during mitosis is necessary to ensure the orderly and accurate separation of the sister chromatids to opposite ends of the cell.

Step-by-step solution

Understand the different phases of the cell cycle

In eukaryotic cell division, the cell cycle is primarily divided into two major phases, Interphase and Mitotic (M) phase. Interphase consists of three substages - the Gap 1 (G1), Synthesis (S), and Gap 2 (G2) phases. Chromosomal compaction level varies in different phases, with least compaction found in G1 phase of Interphase.

Understand compaction levels during the cell cycle

As the cell moves from G1 phase to S phase during Interphase, the DNA replicates, and the chromosome starts to pack into a more compact form. Further compaction takes place in the G2 phase as the cell prepares to enter the M phase, which includes Mitosis and Cytokinesis. During prophase, the first stage of mitosis, chromatin fibers become more coiled and condensed to form distinct chromosomes.

Explain the necessity for further chromatin compaction during mitosis

The necessity for the high degree of compaction achieved during mitosis is to facilitate the orderly separation of the sister chromatids to opposite ends of the cell during anaphase. Without such compaction, it would be more challenging to untangle and split chromosomes without breakage or errors occurring, which could lead to serious genetic abnormalities.