Chapter 11_DNA Replication

Question 1

Template Strands

Answer 1

(Parental Strands) During the replication process, the two complementary strands of DNA come apart and serve as template strands for the synthesis of two new strands of DNA.

Question 2

After the double helix has separated…

Answer 2

…individual nucleotides have access to the template strands.

Question 3

To complete the replication process…

Answer 3

…a covalent bond is formed between the phosphate of one nucleotide and the sugar of the previous nucleotide.

Question 4

Daughter Strands

Answer 4

The two newly made strands after replication.

Question 5

Semiconservative Model

Answer 5

The double stranded DNA is half conserved following the replication process. In other words, the newly made double stranded DNA contains one parental strand and one daughter strand.

Question 6

Origin of Replication (oriC)

Answer 6

The site on the chromosome where DNA synthesis begins

Question 7

DNA replication is initiated by…

Answer 7

…the binding of DnaA proteins to seuqences within the origin known as DnaA box sequences.

Question 8

Which bonds are stronger, the AT or GC region?

Answer 8

The GC. Because only two hydrogen bonds form between AT base pairs, whereas three hydrogen bonds occur between G and C, the DNA strands are more easily separated at an AT-rich region.

Question 9

• DnaA protein

- DnaC protein

Answer 9

• DnaA protein: Binds to DnaA boxes within the origin to initiate DNA replication
• DnaC protein: Aids DnaA in the recruitment of DNA helicase to the origin

Question 10

Dna helicase (DnaB)

Answer 10

Separates double-stranded DNA

Question 11

Topoisomerase

Answer 11

(Type II, or DNA gyrase) Removes positive supercoiling ahead of the replication fork

Question 12

Single-strand binding protein

Answer 12

Binds to single-stranded DNA and prevents it from re-forming a double-stranded structure

Question 13

Primase

Answer 13

Synthesizes short RNA primers

Question 14

DNA polymerase III

Answer 14

Synthesizes DNA in the leading and lagging strands

Question 15

DNA polymerase I

Answer 15

Removes RNA primers, fills in gaps with DNA

Question 16

DNA ligase

Answer 16

Covalently attaches adjacent Okazaki fragments

Question 17

Tus

Answer 17

(Termination Utilizatino Substance) Binds to ter (termination sequences) sequences and prevents the advancement of the replication fork

Question 18

RNA primers

Answer 18

They start, or prime, the process of DNA replication.

Question 19

• Leading Strand

- Lagging Strand

Answer 19

• Leading Strand: A single primer is made at the OriC

- Lagging Strand: Multiple primers are made.

Question 20

DNA Polymerase I, II, III, IV, V

Answer 20

• I and III are involved in normal DNA replication

- II, IV, and V play a role in DNA repair and the replication of damaged DNA.

Question 21

To complete the synthesis of Okazaki fragments within the lagging strand, three additional events must occur:

Answer 21

Removal of the RNA primers, synthesis of DNA in the area where the primers have been removed, and the covalent attachment of adjacent fragments of DNA.

Question 22

Fidelity

Answer 22

DNA synthesis occurs with a high degree of accuracy or fidelity.

Question 23

Proofreading function

Answer 23

Occurs by the removal of nucleotides in the 3’ to 5’ direction at the 3’ exonuclease site.

Question 24

Describe differences between prokaryotic and eukaryotic DNA replication

Answer 24

• Prokaryotic: One OriC.

- Eukaryotic: Multiple OriC

Question 25

ARS elements

Answer 25

(Autonomously replicating sequences) Replication origins that are necessary to initiate chromosome replication. They contain a higher percentage of A and T bases.

Question 26

Prereplicatino complex

Answer 26

(preRC) DNA replication in eukaryotes begins with the assembly of a preRC. Part of the preRC is a group of proteins called the origin recognition complex (ORC) that acts as the initiator of eukaryotic DNA replication.

Question 27

MCM helicase

Answer 27

The binding of MCM helicase at the origin completes a process called DNA replication licensing.

Question 28

Flap endonuclease

Answer 28

Removes small pieces of RNA flaps that are generated by thea ction of DNA polymerase.

Question 29

Telomerase

Answer 29

Prevents chromosome shortening. It recognizes the sequences at the ends of eukaryotic chromosomes and synthesizes additional repeats of telomeric sequences.