Unit 2: Ch. 10a

Question 1

The accepted model for this replication in viruses, prokaryotes, and eukaryotes is…

Answer 1

semiconservative replication

Question 2

in semiconservative replication each replicated DNA molecule consists of…

Answer 2

one “old” and one “new” strand and is thus called semiconservative replication

Question 3

Meselson-Stahl experiment (1958) demonstrated that…

Answer 3

DNA replication is semiconservative in E. coli

Question 4

what does the second generation of semiconservative DNA replication look like? How does it work?

Answer 4

There would be a set of DNA strands that are completely made up of new DNA (Blue) made up of the 1st generation

Question 5

semiconservative replication is also possible in…

Answer 5

eukaryotes

Question 6

In bacteria, DNA replication begins at the origin of replication and is

Answer 6

bidirectional

Question 7

what enzyme is responsible for the 5’ to 3’ polymerization

Answer 7

DNA polymerase III

Question 7

how does chain elongation work?

Answer 7

Chain elongation occurs in the 5’ to 3’ direction by addition of one nucleotide at a time to the 3’ end

Question 8

what is the 3’ to 5’ exonuclease

Answer 8

acts as a first line of defense in correcting DNA polymerase errors by backing up and correcting incorrect bases

Question 9

Which enzyme is mainly responsible for adding new DNA nucleotides during DNA replication in E. coli?

Answer 9

DNA Polymerase III

Question 10

which DNA polymerases have 3’ to 5’ exonuclease activity that allows proofreading?

Answer 10

all of them do lol

Question 11

what is responsible for the initial steps in unwinding a DNA helix? How does it do so, and what follows after?

Answer 11

the protein DnaA. DnaA binds to the origin of replication, and subsequent binding of DnaB and DnaC further opens and destabilizes the helix

Question 12

Proteins which require the energy normally supplied by the hydrolysis of ATP to break hydrogen bonds and denature the double helix, are called…

Answer 12

helicases

Question 13

what are helicases?

Answer 13

DNA helicases catalyze the disruption of the hydrogen bonds that hold the two strands of double-stranded DNA together

Question 14

what prevents supercoiling from happening?

Answer 14

DNA topoisomerase

Question 15

What enzyme provides DNA polymerase III to elongate a polynucleotide chain?

Answer 15

RNA primase

Question 16

what does RNA primase do?

Answer 16

synthesizes an RNA primer that provides the free 3’-hydroxyl required by DNA polymerase III

Question 17

as the replication fork moves, only one strand can serve as a template for _____ DNA synthesis

Answer 17

continuous

Question 18

the strand that has continuous DNA synthesis is called the _____ strand

Answer 18

leading

Question 19

the discontinuous DNA synthesis strand is called the _____ strand

Answer 19

lagging

Question 20

why can only one strand be replicated continuously?

Answer 20

DNA polymerase III only works in the 5’ to 3’ direction

Question 21

the lagging strand is synthesized in pieces called

Answer 21

Okazaki fragments

Question 22

T/F each Okazaki fragment has an RNA primer

Answer 22

true

Question 23

what enzyme removes the primers on the lagging strand?

Answer 23

DNA polymerase I

Question 24

what enzyme joins Okazaki fragments on the lagging strand?

Answer 24

DNA ligase

Question 25

how are both DNA strands synthesized concurrently?

Answer 25

by looping the lagging strand to invert the physical but not biological direction of synthesis

Question 26

What is the major difference between the lagging and leading strands?

Answer 26

DNA polymerase is able to continuously add new nucleotides on the leading strand while it must keep ‘starting over’ on the lagging strand

Question 27

DNA synthesis at a single replication fork involves these enzymes (6)

Answer 27

• DNA helicases
• DNA gyrase
• RNA primase
• DNA polymerase I
• DNA polymerase III
• DNA ligase