Okazaki Fragments in Lagging Strand Synthesis

Steps:

• Lagging strand is synthesized discontinuously due to antiparallel DNA structure and 5' to 3' polymerase directionality.
• Short RNA primers initiate each segment, followed by DNA synthesis toward the primer.
• These segments, called Okazaki fragments, have an RNA primer at the 5' end and DNA extending to the 3' end.
• DNA ligase seals nicks after primer removal and gap filling.

Why D is correct:

• Okazaki fragments contain an RNA primer at the 5' end and are synthesized in the 5' to 3' direction, matching the DNA polymerase mechanism.

Why the others are wrong:

• A: Incorrectly states synthesis in 3' to 5' direction, violating polymerase rules.
• B: Wrongly places RNA primer at the 3' end, as primers initiate at the 5' end.
• C: Falsely describes full DNA fragments without RNA primers, ignoring initiation process.

Final answer: D