DNA replicates before a cell divides to give a complete set of genetic instructions to each daughter cell.
If a cell begins meiosis without duplicating its DNA, the two resulting cells would have insufficient DNA to develop properly, as there would only be one copy of each chromosome in the parent cell. So as the division occurs, half of the DNA needed would go to one cell, and another half to the other. This means that there would be insufficient data to develop properly. This would most likely result in the cells dying off.