All cells contain DNA. It is the genetic material which is passed down from the cell to its daughter cells.
simply put DNA is a storage house. It contains all the information needed to make a protien that the cell needs. We know that protiens are thw building blocks of a cell and many protiens needs to be made within the cell so DNA is one of the, if not the most important part of the cell.
It not only contains information to make protiens but also to control and regulate them. It also contains the information passed down from generations (like mutation or info needed to adapt to situations or resistance etc). so if the cell needs to divide to make offsprings it is of vital importance that they copy and give this DNA to their daughters . That is what it makes the genetic material of the cells. What the daughter will inherit from its parent cell. So DNA is what makes the cell what it is. Do you know that different cell has different DNAs. So it also act as a uniqueness of the cell.
Simply put dna is the central part of the cell