DNA Replication

Steps to DNA Replication (3. Joining)

DNA Polymerase removes RNA Primer and fills its place with DNA nucleotides DNA ligase links the Okazaki Fragments.

Steps to DNA Replication (1. Unwinding)

DNA helicase (enzyme) unwinds and unzips the DNA - breaking the hydrogen bonds between the strands Single-stranded binding proteins (SSB)- go to DNA strand to keep them separated during replication. RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand. DNA unwinds at different spots (Origins) At the replication fork, an enzyme (Helicase) breaks the hydrogen bonds between the bases

Steps to DNA Replication (2. Base Pairing)

DNA polymerase (enzyme) adds complementary nucleotides to parent DNA strand Only adds in the 5' to 3' direction!!!!! Two daughter strands of DNA are made differently Leading Strand- Elongated as the DNA unwinds. Built continuously without breaks Lagging Strand- Elongates AWAY from replication fork. Built discontinuously makes several small fragments of DNA called Okazaki Fragments

Mistakes in DNA

DNA replication takes a lot of energy During replication, mistakes are made (mutations) Enzymes "proof read" and repair the mistakes: Ex: DNA polymerase, exonuclease

Eukaryotes vs. Prokaryotes

Eukaryotic DNA unwinds in multiple areas as DNA is replicated. In prokaryotes, the circular DNA strand is opened at one origin of replication.

Enzymes involved

Helicase- unzips the DNA strand Primase- adds RNA Primer (tells the next enzyme where to begin!) DNA polymerase- adds new nucleotides DNA ligase- links together fragments

Semiconservative Replication

Parental strands of DNA separate Each strand serves as template DNA molecules produced have one strand of parental DNA (old) and one daughter strand (new): "semi"- half "conserve"- save