Is it gene is the smallest part of the cell?

No, a gene is not the smallest part of a cell; rather, it is a segment of DNA that encodes information for the synthesis of proteins. The smallest unit of a cell is typically considered to be the cell itself, while at a molecular level, the smallest components would be molecules such as nucleotides (which make up DNA) or even atoms. Genes are essential for cellular function, but they are part of larger structures within cells.