BiologyChapter 12, Section 2

Semiconservative Replication

Main idea-DNA replicates by making a strand that is complementary to each original strand.

Objectives What is their role of enzymes in the replication of DNA? How are leading and lagging strands synthesized differently? How does DNA replication compare in eukaryotes and prokaryotes?

Review Vocabulary Template: a molecule of DNA that is a pattern for synthesis of a new DNA molecule.

New Vocabulary Semiconservative replication DNA polymerase Okazaki fragment

I. Semiconservative Replication Overview A. Parental ______________________ of DNA separate, serve as ______________________,

and produce DNA molecules that have one strand of ______________________ DNA and one strand of ______________________ DNA.

B. Three Steps:i. Unwinding: DNA is ______________________ to prepare for replication

ii. Base pairing: new strands of DNA are added to ______________________ DNA strand

iii. Joining: Okazaki fragments are ______________________ together by DNA ligase

II. UnwindingA. DNA helicase, an ______________________, is responsible for ______________________

and unzipping the double helix. B. RNA primase adds a short ______________________ of RNA, called an RNA

______________________, on each DNA strand.

III. Base PairingA. DNA polymerase continues ______________________ appropriate nucleotides to

the ______________________ by adding to the 3′ end of the ______________________ DNA strand.

B. One strand is called the ______________________ strand and is elongated as the DNA ______________________.

i. The leading strand is ______________________ in a 5’ to 3’ direction. C. The other strand of DNA, called the ______________________ strand, elongates

______________________ from the replication fork. i. The lagging ______________________ is oriented in a 3’ to 5’ direction.

ii. The lagging strand is ______________________ discontinuously into small segments, called Okazaki fragments.

IV. JoiningA. DNA ______________________ removes the RNA primer and ______________________ in

the place with DNA ______________________. B. DNA ligase ______________________ the two sections.

V. Comparing DNA Replication in Eukaryotes and ProkaryotesA. Eukaryotic DNA ______________________ in multiple areas as DNA is

______________________. B. In prokaryotes, the circular DNA strand is opened at ______________________

origin of ______________________.