1 Singlestrand nicks made by separate the two strands in a D

1) Single-strand nicks made by ________________________separate the two strands in a DNA molecule in the absence of rotation.

type II topoisomerases

type I topoisomerases

single strand breaking proteins (SSBs)

displacement enzymes

2)

Which of the following is true?

Flap endonuclease and DNA Pol I use 5\' to 3\' exonuclease to remove RNA primers

Both eukaryotes and bacteria need a non-processive polymerase in order to remove RNA primers.

DNA Pol I has 3\' to 5\' exonuclease activity but DNA Pol III does not.

DNA Pol I uses 5\' to 3\' exonuclease activity to remove RNA primers but DNA Pol epsilon and DNA Pol delta do not.

Solution

Question number 1 : The correct answer is B ( type I topoisomerase)

Explanations : There are two classes of topoisomerases. Type I topoisomerases act by transiently breaking one of the two DNA strands, passing the unbroken strand through the break, and rejoining the broken ends; they change Lk in increments of 1. Type II topoisomerases break both DNA strands and change Lk in increments of 2.

Lk : Linking number