Which enzyme chemically links DNA fragments together (Okazaki fragments)?

Which enzyme chemically links DNA fragments together (Okazaki fragments)?

• A. Unzips DNA strands
• B. Enzyme that chemically links DNA fragments together (Okazaki fragments)
• C. Synthesizes RNA primer
• D. Binds DNA to histones

Answer: (B)

This question tests how the lagging strand is built during DNA replication. Okazaki fragments are short pieces synthesized in the 5' to 3' direction, and they must be joined to form a continuous strand. The enzyme that does this is DNA ligase, which seals the nicks between fragments by forming phosphodiester bonds, effectively linking the pieces together. Helicase unzips the DNA, primase lays down RNA primers to start synthesis, and histones bind DNA to organize chromatin; none of these directly join the fragments. So the enzyme that chemically links the fragments is DNA ligase.

This question tests how the lagging strand is built during DNA replication. Okazaki fragments are short pieces synthesized in the 5' to 3' direction, and they must be joined to form a continuous strand. The enzyme that does this is DNA ligase, which seals the nicks between fragments by forming phosphodiester bonds, effectively linking the pieces together. Helicase unzips the DNA, primase lays down RNA primers to start synthesis, and histones bind DNA to organize chromatin; none of these directly join the fragments. So the enzyme that chemically links the fragments is DNA ligase.