Bacteria generally have a single chromosome that is in shape and found in the nucleoid region of the cell. Before the cell undergoes , the chromosome must so each daughter cell receives an identical copy of the genome. During this process, which proceeds in the direction, one strand is synthesized continuously and is known as the while the other strand, known as the , must be made in fragments. All the individual fragments are eventually joined together by , an enzyme that can create a covalent bond between adjacent bases. An exact copy of the parental strands is made because of the base-pair arrangement in the strands; adenine always pairs with and guanine always pairs with . The enzyme limits the occurrence of mutations by proofreading for mistakes. In order to make proteins, the strand of DNA is used during to synthesize a copy of the gene in the form of , which is identical to the coding strand of DNA except replaces .