Final answer:
During cell division, the structure that becomes tightly packed and contains DNA is called the chromosome.
Step-by-step explanation:
During cell division, the structure that becomes tightly packed and contains DNA is called the chromosome. Chromosomes are formed when the long strands of DNA are wrapped around proteins called histones, which are then bundled and condensed into a compact structure. This compacted form of DNA allows for efficient segregation of genetic material during cell division.