What is lagging strand synthesis?


Quick Answer

Lagging strand synthesis is the creation of a complementary DNA strand on the lagging strand of DNA. When DNA is being replicated, the DNA molecule unzips a little at a time, with one strand labeled the "leading strand," while the other is the "lagging strand."

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Full Answer

Each strand of DNA dictates the synthesis of a complementary strand. Each original strand and its complement become an entire DNA molecule. As the DNA molecule unzips, the complement to the leading strand forms along the replication fork, the "Y" junction at which the DNA is unzipping. The complement of the lagging strand forms in short spurts, called "Okazaki fragments." An enzyme, RNA primase, must first put down a short sequence of RNA, called a "primer." It is complementary to a section of the lagging strand of DNA. The enzyme that synthesizes a complementary DNA strand, DNA polymerase III, needs an RNA primer before it can start making DNA. The last enzyme, DNA ligase, joins the ends of the Okazaki fragments together to form a continuous DNA strand.

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