10.4-10.5 Warm-Up
1.Briefly describe the process of DNA replication.
2.How fast are nucleotides added as your DNA
replicates?
3.Describe a replication bubble. Why are numerous
bubbles forming at once helpful?
4.What is DNA polymerase? DNA ligase?
DNA replication depends on
specific base pairing
Section 10.4
DNA Replication
A
A
Nucleotides
Parental molecule
of DNA
Both parental strands serve
as templates
Enzymes use each strand as a template to assemble the new strands
Two identical daughter
molecules of DNA
DNA Replication
Untwisting and replication of DNA
DNA replication: A closer look
Section 10.5
Parental strand
Origin of replication
Daughter strand
Bubble
Two daughter DNA molecules
DNA Replication Begins at Specific Sites
5ʹ′ end
3ʹ′ end
P
P
P
P
P
P
P
P
Each strand of the double helix is oriented in the opposite direction
DNA Polymerase
• enzyme that links DNA nucleotides to a growing
daughter strand
• can only add to the 3’ end of parent strand
• the new strand then grows in the 5’ to 3’
direction
DNA Polymerase
• proofreads new DNA strand (and fixes incorrect
pairings)
• can repair damaged DNA segments
damage caused by radiation, ultraviolet light, toxic chemicals
DNA polymerase
5ʹ′ end
molecule
3ʹ′
5ʹ′
Parental DNA
5ʹ′
3ʹ′
Daughter
strand
synthesized
in pieces
3ʹ′
5ʹ′
P
3ʹ′
5ʹ′
5ʹ′
3ʹ′
Daughter strand
synthesized
continuously
P
DNA ligase
Overall direction of replication
DNA daughter strands are synthesized 5’ to 3’
lagging
strand
3ʹ′
5ʹ′
DNA Ligase
• enzyme that ties the together short pieces of DNA
nucleotides into one single DNA strand (on lagging
strand)
• can repair damaged DNA
damage caused by radiation, ultraviolet light, toxic chemicals
Homework:
• Packet Section 3,4
• Read 10.6-10.7