dna replication

Conservative model

both strand serve as a template for DNA synthesis

Semi-conservative model

one strand serves as a template for DNA synthesis

Dispersive model

parental DNA is dispersed randomly from each strand during DNA synthesis

Meselson and Stahl

preformed an experiment to determine which DNA replication model is correct

Cesium Chloride Gradient

a gradient in which different densities of DNA will settle in specific places in the tube

Buoyant density

Density at which DNA floats in a gradient. heavy labeled DNA runs further

DNA fiber autoradiography

nucleotides are radiolabeled so that DNA replication/synthesis can be observed

Bi-directional

DNA synthesis begins at the origin of replication and replication forks unwind the DNA outwards in both directions

Replicon model

model for DNA replication in which an initiator binds to the origin of replication and the replication forks move outward from the origin in a bidirectional fashion

Initiator

proteins that bind to the origin and initiate replication

Replicator

the origin of replication

Origin of replication

the sequence where DNA replication takes place

DNA helicase

unwinds the parental DNA strand by breaking the H-bonds between nucleotides

Single-Stranded binding (SSB) proteins

coat the ssDNA to keep the strands apart and protect the ssDNA

DNA polymerase III

attaches to an RNA primer and synthesizes DNA, can excise an incorrect base pair in a proofreading function.

Primase

Synthesizes the RNA primer at the origin on both parental strands

RNA primer

a synthesized free 3'-OH and triphosphate nucleotide that DNA polymerase III can attach to

Leading strand

The continuously synthesized strand made by DNA pol III

Continuous strands

the strand that is synthesized continuously, leading strand

Lagging strand

the strand that must be unwound and have RNA primers placed on it, synthesized discontinuously in Okazaki fragments

Discontinuous strand

synthesized in segments or fragments, lagging strand

Okazaki fragments

small fragments of synthesized DNA interrupted by RNA primers, DNA pol III extends until it hits the previous primer

Semi-discontinuous

DNA is synthesized in a continuous and discontinuous fashion

DNA replication bubble

a section of unwound parental DNA used to synthesize new DNA

Proofreading

the ability of DNA pol III to excise an incorrect base pair and add the correct base

Exonuclease

removing a base from the 3' end

DNA polymerase I

removes the RNA primer and fills in the gap with DNA nucleotides

DNA ligase

covalently links Okazaki fragments together

Replication fork

move away from the origin in a bidirectional fashion, where DNA is unwound

Replisome

a large complex of proteins that preform DNA replication at the replication fork