What is the portion of the cell cycle during which the chromosomes are invisible under the light microscope because they are not yet condensed

Interphase

Explanation:

The portion of the cell cycle during which the chromosomes are invisible under the light microscope is the interphase.

Generally, there are 2 main phases of the cell cycle, namely;

1. The interphase

2. The m phase

The interphase is further subdivided into 3 phases:

The m phase represents the active division phase, also known as mitosis.

Immediately the cell leaves the interphase for the  m phase, the genetic materials in the cell condense, thicken, and become visible under the microscope as chromosomes. This phase of mitosis is known as the prophase and the chromosomes remain visible through the rest of the mitotic phase (metaphase, anaphase) until the last phase, which is the telophase/cytokinesis.

At telophase/cytokinesis, the chromosomes condense back and the daughter cells produced enters the interphase for a repetition of the cycle.

it is called the mitotic spindle