Pp 295 - 301. 2. Replication Elongation DNA polymerase – enzyme which does what? In what...

DNA Replication Elongationpp 295 - 301

2. Replication ElongationDNA polymerase – enzyme which does what? In what

direction? What is the main version responsible for replication?in prokaryotes: DNA polymerase I, II, III, IV & Vin eukaryotes: over 15 different types

Nucleotide chains only form in the 5’ 3’ direction.

DNA Polymerase III Substrates1. DNA template2. deoxyribonucleoside triphosphates (dNTPs)

3. RNA primer

5’3’

5’3’

5’ 3’

2. Replication Elongation1. Primase:

5’3’

5’ 3’

A

2. Replication ElongationThree steps involved in the addition of every

nucleotide to the new piece of DNA are:

AT

TTP P P

2. Replication Elongation

2. Replication ElongationIn what direction must the DNA polymerase produce

the new strand of DNA?

Which direction does the replication fork open?

2. Replication ElongationProkaryotic DNA is circular. Two DNA polymerases

replicated in opposing directions until both strands are completed.

2. Replication ElongationEukaryotic DNA is linear. DNA polymerases in travel

both directions from the ori site.

What direction is DNA synthesized?

Leading Strand

5’

5’

3’

3’

helicase

SSBPs

gyrase

primase

5’

3’

DNA polymerase III

Lagging Strand

Okazaki fragment

5’

3’

5’

3’

5’

3’

helicasegyrase

2. Replication ElongationOkazaki fragments:

DNA polymerase I –

DNA ligase –

2. Replication ElongationDNA replication occurs:

1. continuously on the _______ strand

2. discontinuously on the _______ strand

Replication Animation

3. Replication TerminationTelomeres

TTAGGG

Telomeres

TelomeraseExplain what happens to the telomere during each

round of replication, why this is important and why some cells have a mechanism to repair this while others do not…

TelomeraseTelomeres and aging?

TelomeraseTelomerase:

Mistakes in DNA ReplicationFewer than 1 error in 107 NTs

Exonuclease –

Roles of DNA polymerase I and II

ClassworkIntroduce yourself to your neighbor

Everyone get into groups of 2-3

In groups, summarize DNA replication as a series of steps