Dna coils tightly during division and assembles into visible

chromosomes

Explanation:

DNA of organisms is organized into one or more thread-like structures called chromosomes. Chromosomes are made of DNA and its packing proteins.  During cell division, the thin mass of chromatin which in turn is made of DNA and its packing protein condense and becomes visible as individual chromosomes. The DNA molecule is wrapped around histone proteins to form nucleosomes which in turn become compact into chromatin fibers.

The further condensation of looped domains formed by the coiling of chromatin fiber forms chromosomes. The part of a chromosome that holds its two arms together is called centromere. Chromosome becomes visible during the prophase stage only when condensation of chromatin takes place.