The enzymes responsible for copying DNA are described as which of the following?

• A. A series of enzymes that unzip DNA and attach complementary bases
• B. Proteins that fold the DNA
• C. RNAs that translate DNA
• D. Lipids that store energy

Answer: (A)

DNA copying relies on an enzyme system that unzips the double helix and builds new strands by pairing each base with its complement. This description fits the replication machinery that first separates the two strands and then attaches complementary bases to form new strands. Helicase unwinds the helix, primase lays down RNA primers, DNA polymerase adds nucleotides in the 5' to 3' direction, and ligase seals the fragments on the lagging strand. Other options miss this essential copying process: proteins that fold DNA relate to structure rather than replication; RNAs that translate DNA describe gene expression rather than copying; lipids that store energy are unrelated to DNA replication.