lecture 21

Question 1

where does helicase bind to

Answer 1

helicase bind to the lagging strand

Question 2

how many polymerase are there in the E.coli

Answer 2

5 polymerase

Question 3

which polymerases are replicable polymerases

Answer 3

polymerase 1 and 3

Question 4

which polymerase do the DNA repair functions

Answer 4

polymerase 2, 4 and 5

Question 5

what are the activities of DNA Polymerases I

Answer 5

Pol. I -aids in removal of RNA primers has 5’ to 3’ polymerase and 5’ to 3’ exonuclease
activity Proofreading: has 3’ to 5’ exonuclease activity not highly processive; short tract synthesis

Question 6

what are the activities of DNA Polymerases III

Answer 6

main replicative polymerase; highly processive
-has 5’ to 3’ polymerase activity
-lacks 5’ to 3’ exonuclease activity
-Proofreading: has 3’ to 5’ exonuclease activity

Question 7

what is the β sliding clamp

Answer 7

The β sliding clamp is a ring-shaped polypeptide that encircles the DNA and interacts with DNA polymerase III to enhance
processive DNA synthesis.

Question 8

what does single strand DNA binding protein do

Answer 8

single strand DNA binding protein keeps the unwound strands in an extended form for replication

Question 9

how do polymerase 1 and 3 co operate

Answer 9

*when DNA synthesis by Pol. III reaches the 5’ end of the RNAprimer,
Pol. III is “swapped” for Pol. I.
*DNA Polymerase I (which has 5’ to 3’
exonuclease activity AND 5’ to 3’
polymerase activity) removes the RNA
primer and re-synthesizes a short
tract of DNA.

Question 10

what does DNA ligase do

Answer 10

DNA ligase makes a phosphodiester
bond between the 5’ phosphate and
the 3’ OH group.