At the beginning of cell division (specifically during prophase), each chromosome consists of two identical sister chromatids held together at the centromere.

Here's a breakdown:

* Chromatid: Each chromatid is a copy of the original DNA molecule. They are essentially identical copies of the genetic material.

* Centromere: This is the specialized region of the chromosome that connects the two sister chromatids. It's also the point where spindle fibers attach during cell division, ensuring proper chromosome separation.

So, to summarize, at the beginning of cell division, each chromosome is essentially a double-stranded structure, with the two identical strands (sister chromatids) linked at the centromere.