dna, and in some cases rna, is the primary source of ... · okazaki fragments the lagging strand is...

DNA REPLICATIONDNA, and in some cases RNA, is the primary source of heritable information.

The “Central Dogma”Replication

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DNA ReplicationAllows for heritability of genetic information.

Happens “Semi-conservatively”

Each strand of an old molecule serves as a template for the synthesis of a new strand.

The ReplisomeAll of the enzymes involved in replication function together.

Helicase: Topoisomerase: Opens the helix. Rotates the helix.

Ligase: Joins DNA fragments

Primase: Synthesizes RNA primer

DNA PolymeraseResponsible for the addition of new nucleotides to a growing strand.

Can only add nucleotides in the 5’ → 3’ direction.

Makes mistakes.

Directional Synthesis 5’→3’Polymerase can only make new strands in the 5’ → 3’ direction.

Leading strand: synthesized continuously in 1 piece.Lagging strand: synthesized discontinuously in multiple fragments, connected by ligase.

Okazaki FragmentsThe lagging strand is synthesized discontinuously, as a series of segments called Okazaki fragments

Proofreading and Repairing DNANuclease – an DNA cutting enzyme that cut outs (excised) damage DNA

Telomeres – repetitive DNA at the end of eukaryotic chromosome’s DNA molecule that protects genes from being eroded through repetitive replication