W - BIOL200 - 3.3 IN VIVO DNA REPLICATION

Where does replication begin?

At origins of replication.

How many origins do prokaryotes have?

 One.

How many origins do eukaryotes have?

Multiple.

What are replication bubbles?

 Opened regions where DNA is replicating.

Name of prokaryotic origin of replication?

Ori.

What enzyme unwinds DNA?

Helicase

What protein prevents strand reannealing?

 Single-stranded binding protein (SSB).

What enzyme relaxes supercoils?

 Topoisomerase.

 What enzyme synthesizes new DNA?

DNA polymerase III.

 What enzyme creates the RNA primer?

 Primase.

What direction does DNA polymerase read DNA?

3' → 5'.

What direction does it synthesize DNA?

5' → 3'.

What enzyme removes RNA primers?

 DNA polymerase I (prokaryotes), RNase H (eukaryotes).

What enzyme joins Okazaki fragments?

DNA ligase.

What holds DNA polymerase in place?

Sliding clamp protein.

 Leading strand moves in what direction?

 Toward replication fork.

Lagging strand moves in what direction?

 Away from replication fork.

What are Okazaki fragments?

 Short DNA segments on the lagging strand.

How long are Okazaki fragments?

About 100–200 base pairs.

What connects Okazaki fragments?

DNA ligase after RNA primer is replaced.

 Number of DNA polymerases in prokaryotes?

5.

Number of DNA polymerases  in eukaryotes?

14.

Rate of replication in prokaryotes?

 ~1000 nucleotides/sec.

Rate of replication in eukaryotes?

50–100 nucleotides/sec.

 Enzyme for strand elongation (eukaryotes)?

 DNA Pol α, Pol δ, Pol ε.

Main elongation enzyme in prokaryotes?

DNA Pol III.