DNA must be packaged but packing must be orderly so that genes can be opened up when they need to be transcribed and repackaged when they don't. DNA is complexed with proteins to form chromosomes. The specialty of examining chromosomes in the microscope for damage or defect is called Cytogenetics.
Chromosomes exist in different states throughout the cell cycle.
Highly condensed chromosomes occur only for a brief period of time. Interphase chromatin contains both extended regions and regions that remain condensed at all times, called heterochromatin. Females have 1 inactive X chromosome composed completely of heterochromatin. Even though it is not condensed, interphase chromatin is specifically organized in the nucleus. The cell cycle is the cycle of duplication of cellular components followed by cell division.