Explain how DNA is involved in cell division (including the replication of DNA before cells divide during mitosis) and protein synthesis (including transcription and translation of genes).

This question is asking for two different things. The first deals with the cell cycle, which involves interphase, mitosis, and cytokinesis. Interphase can be divided into three sub-phases called gap 1, synthesis, and gap 2. In regard to this question, the synthesis phase is what to examine. In broad terms, interphase is cell growth, and mitosis is cell reproduction; however, before a cell can split, it needs to manufacture an additional set of chromosomes/DNA so that each daughter cell ends up with the full compliment of DNA. The cell will do this during the synthesis phase. The general idea is that the DNA double helix will "unzip" itself, and new bases will be inserted along each half in a way that matches adenine to thymine and guanine to cytosine. Once a full copy of the DNA has been produced, mitosis can begin by breaking down the nuclear membrane. From there, the chromosomes will line up across the cell's equator, and the centrioles will pull a full set of DNA to opposite sides of the cell before the cell membrane pinches completely off during telophase and cytokinesis.
The other part of the question deals with the DNA message being copied and turned into an mRNA strand. That process is called transcription. The mRNA strand will then leave the cell nucleus and go to a ribosome. The ribosome will translate the RNA message and string together amino acids until a protein is completed.
https://dnalc.cshl.edu/resources/3d/12-transcription-basic.html