DNA Replication

Step1 of DNA Replication: Helicase unwinds and “unzips” the molecule. 5′ end 3′ end Helicase 3′ end 5′ end

Step1 of DNA Replication: Helicase unwinds and “unzips” the molecule. 5′ end 3′ end Helicase 3′ end 5′ end

Step2 of DNA Replication: DNA polymerase adds bases to the template strand starting at the 3′ end and moving toward the 5′ end. 3′ end 5′ end DNA POLYMERASE 3′ end 5′ end

5' 3' Helicase 3' 5'

5' 3' RNA primer 3' 5' 3' “Leading Strand” 3' 5'

5' 3' RNA primer 3' 5' “Leading Strand” 3' 5'

5' 3' 3' 5' “Leading Strand” 5' 3' 5'

“Lagging Strand” “Leading Strand” 5' “Lagging Strand” 3' Okazaki Fragment #1 Okazaki Fragment #2 Okazaki Fragment #3 “Leading Strand” 3' 5'

“Lagging Strand” DNA Ligase 5' “Lagging Strand” 3' Okazaki Fragment #1 Okazaki Fragment #2 Okazaki Fragment #3 DNA Ligase

Overall direction of DNA replication 3′ Overall direction of DNA replication Replication Fork- Site where DNA is being duplicated. 5′ 4 3 3′ 2 Helicase- Unwinds and unzips the DNA. 1 DNA polymerase- Adds new nucleotides to the parental strand of DNA. 5′

Replication Bubble

There are multiple replication bubbles along one strand of DNA

The arrows in this picture are pointing to replication bubbles The arrows in this picture are pointing to replication bubbles. This is a real photograph taken with an electron microscope.