8.2 Study Guide

Question 1

What does it mean to replicate DNA?

Answer 1

to create an exact copy of a DNA molecule

Question 2

What does it mean for DNA replication to be semi-conservative?

Answer 2

Each new DNA molecule formed during replication contains one original (parent) strand and one newly formed strand.

Question 3

How do we know that DNA replication is semi-conservative?

Answer 3

Due to the Meselson-Stahl experiment, which used density labeling to track the fate of DNA strands during replication.

Question 4

Why is it important that DNA replication creates an exact copy?

Answer 4

It is crucial for cell division as it ensures each new cell receives a complete set of DNA instructions

Question 5

When would DNA replication occur?

Answer 5

Before Cell Division in “Interphase”

Question 6

Where would DNA replication occur in Eukaryotic Cells?

Answer 6

The Nucleus

Question 7

Where does DNA replication begin?

Answer 7

Sites called Origins of Replication

Question 8

What is the first step in DNA replication? What enzyme is involved?

Answer 8

Part of the DNA Double Helix is Unwound

Enzyme = Helicase

Question 9

How is the DNA strand stabilized during the first step?

Answer 9

Single-Stranded binding proteins (SSB proteins)

Question 10

What is the replication fork?

Answer 10

Y shaped region where the parental strands of DNA are being unwound

Question 11

What is the second step in DNA replication? What enzyme is involved?

Answer 11

RNA primer is laid down providing a free 3’-hydroxyl group to attach new nucleotides to

Enzyme=Primase

Question 12

Can DNA Polymerase I initiate synthesis on its own?

Answer 12

No, it can only add nucleotides to an existing chain and cannot initiate synthesis on its own

Question 13

Can DNA Polymerase I build onto the 5’ end of an existing DNA strand?

Answer 13

No, only the 3’ end of an existing DNA strand

Question 14

What is the third step in DNA replication? What enzyme is involved?

Answer 14

DNA Nucleotide bases are added to the growing (daughter) strand at the replication fork

Enzyme = DNA Polymerase III

Question 15

Where does the energy for DNA replication come from?

Answer 15

The Phosphate (P-P-P) bonds in nucleosides (ATP, GTP,TTP and CTP)

Question 16

What are nucleosides?

Answer 16

Nucleotides with P-P-P

Question 17

Nucleotides are added to a growing DNA strand by their _______ to the _____ end.

Answer 17

Phosphate

3’

Question 18

DNA stands only grow in this direction?

Answer 18

5’ to 3’

Question 19

Nucleotides need a starter ________ to bond to during replication.

Answer 19

nucleotide

Question 20

What is the fourth step in DNA replication? What Enzyme is involved?

Answer 20

The RNA Primer is replaced by DNA
(happens with replication is almost complete)

Enzyme=DNA Polymerase I

Question 21

What is the fifth step in DNA replication? What Enzyme is invovled?

Answer 21

Okazaki Fragments are glued together to form a continuous strand.

Enzyme = DNA Ligase

Question 22

What are Okazaki Fragments?

Answer 22

Small fragments of DNA in the lagging strand that are generated due to the discontinuous synthesis from the 5’ to 3’ direction

Question 23

What are the five primary enzymes in DNA replication?

Answer 23

1. DNA Helicase
2. RNA Primase
3. DNA Polymerase I
4. DNA Polymerase III
5. DNA Ligase

Question 24

What does DNA Helicase do?

Answer 24

Unwinds and separates double stranded DNA by breaking the H bonds between base pairs

Happens at specific regions and creates a replication fork of two strands running in antiparallel directions

Question 25

Nucleotides have to be added in opposite directions on the two parent strands during DNA replication because?

Answer 25

DNA strands are antiparallel

Question 26

Which direction is DNA Polymerase moving on the leading strand?

Answer 26

Toward the replication fork

Question 27

Is DNA continuous or discontinuous on the leading strand?

Answer 27

Continuous

Question 28

Which direction is DNA Polymerase moving on the lagging strand?

Answer 28

Away from the replication fork

Question 29

Is DNA continuous or discontinuous on the lagging strand?

Answer 29

Discontinuous

Question 30

Why are Primes (3', 5') are used in numbering carbons on the sugar portion of the nucleotide?

Answer 30

to distinguish them from the nitrogenous base carbons

Question 31

Why do you think multiple replication bubbles form during the process of DNA replication?

Answer 31

To significantly speed up the process by allowing for simultaneous replication at various points along the DNA molecule.

Question 32

Why is the helicase able to break the H bonds between base pairs?

Answer 32

It acts as a molecular motor, using energy derived from ATP hydrolysis to physically disrupt the weak hydrogen bonds, allowing the DNA strands to separate and unwind.

Question 33

Does Replication occurs on one side of the replication fork at a time?

Answer 33

No, replication occurs on both sides of the fork simultaneously

Question 34

As a new nucleotide is added to the growing DNA strand, which part of the new nucleotide forms a bond with the 3’ OH group of the existing strand?

Answer 34

5' phosphate group of the new nucleotide forms a bond with the 3' OH group of the existing strand.

Question 35

What does DNA Polymerase III do?

Answer 35

Main DNA Builder 1000 bases/ second

Question 36

What does DNA Polymerase 1 do?

Answer 36

Proofreads and corrects typos Repairs Mismatched Bases Removes Abnormal Bases Overall reduces error rates from 1 in 10,000 to 1 in 100 million bases RNA Primer removal

Question 37

In DNA Synthesis, the DNA template strand is read in the ______ direction, while the new strand is made in the direction.

Answer 37

3' to 5' 5' to 3