[IB Biology, Chapter 14: Replication]

Replication

Terminology:

Helicase: Enzyme that unwinds the DNA double helix and separates it into two sides.

Replication Fork: The Y formed as helicase opens the DNA molecule.

Leading Strand: The new DNA molecule forming towards the replication fork along the old strand (in the 5' -----> 3' direction).

Lagging Strand: The new DNA molecule forming away from the replication fork along the lower, old strand (in the 5' -----> 3' direction). Must be built of several 100 - 200 nucleotide segments called Okazaki fragments.

rRNA Primer: Sequence of about 10 RNA nucleotides placed at the 5' end of the new DNA strand. The DNA Polymerase then bonds to this to initiate placement of new DNA nucleotides. The RNA nucleotides will eventually be removed and replaced with DNA nucleotides.

DNA Polymerase III: DNA replicating enzyme (places complementary DNA nucleotides along old DNA template strand.).

DNA Ligase: Enzyme that bonds Okazaki fragments to the lagging strand.

[Simpler View of Replication]

A Site with a good beginning Animation of Replication (Needs Shockwave)

Long & Slichter