DNA Replication - POB I

DNA polymerase

An enzyme that catalyzes the formation of phosphodiester linkages between deoxyribonucleotides, forming the primary structure of DNA.

DNA ligase

An enzyme that catalyzes the formation of phosphodiester linkages in gaps between two existing nucleotides in double-stranded DNA.

Origin of replication

A location (a point) where enzymes open the DNA double helix so replication can begin.

Replication fork

The y-shaped structure visible in micrographs of DNA during replication. This is the site where the replisome works, synthesizing the leading and lagging strands.

Primase

An enzyme that adds a short RNA primer to single-stranded DNA, so DNA polymerase can start adding complementary bases.

Replisome

The multi-molecular machine that works at the replication fork, copying DNA

Helicase

An enzyme in the replisome that opens the DNA double helix, creating single-stranded template DNA for leading and lagging strand synthesis.

Topoisomerase

An enzyme that is important in DNA replication. It breaks and rejoins DNA to relieve the tension created when helicase continuously opens the double helix.

Telomerase

An enzyme that catalyzes the addition of deoxyribonucleotides to lagging strands at either end of a linear chromosome, thus helping to solve the end-replication problem.

Stem cells

A “professional divider” cell. After each round of mitosis and cell division, one daughter cell becomes a stem cell and the other becomes a specialized cell type that no longer divides. Different types of stem cells give rise to daughter cells which then mature into specific cell types.

DNA proofreading

The ability of DNA polymerase to respond when it adds the wrong base by mistake by 1) pausing synthesis of the new strand, 2) removing the mismatched base with an exonuclease activity, and 3) adding the correct base.

DNA mismatch repair

Proteins and enzymes work on newly synthesized DNA molecules to recognize and repair mismatched bases.

DNA excision repair

Proteins and enzymes work on DNA molecules long after replication is complete to recognize and repair damaged areas as they arise.