20.3 - DNA replication

Question 1

The product of this mechanism would be a new DNA molecule in which one strand is the ________-, strand and the second strand is a ____ synthesized, or ____, strand.

Answer 1

parent/original
newly
daughter

Question 2

This mode of DNA replication is called

Answer 2

semiconservative replication

Question 3

In semiconservative DNA replication, each parent strand serves as a

Answer 3

template for the synthesis of a new daughter strand.

Question 4

Bacterial chromosomes are __________ ranging in size from 600,000 to 10,000,000 base pairs.

Answer 4

circular molecules of DNA

Question 5

DNA replication begins at a unique sequence on the circular chromosome known as the

Answer 5

replication origin

Question 6

Replication occurs ______ at the rate of about ________

Answer 6

bidirectionally

500 new nucleotides every second

Question 7

The point at which the new deoxyribonucleotide is added to the growing daughter strand is called the

Answer 7

replication fork

Question 8

It is here that the DNA has been ____ to allow binding of the various proteins and enzymes responsible for ________-

Answer 8

opened

DNA replication

Question 9

Since DNA synthesis occurs bidirectionally, there are ________-moving in ______ directions.

Answer 9

two replication forks

opposite

Question 10

Replication is complete when the replication forks ____ approximately ____around the circular chromosome.

Answer 10

collide

halfway

Question 11

The first step in DNA replication is the

Answer 11

seperation of the DNA strands

Question 12

The protein _____ does this by breaking the _____ between the_____-

Answer 12

helicase
hydrogen bonds
base pairs

Question 13

breaking the h bonds between the base pairs causes

Answer 13

supercoiling of the molecule.

Question 14

This stress is relieved by the enzyme

Answer 14

topoisomerase

Question 15

topoisomerase

Answer 15

travels along the DNA ahead of the replication fork.

Question 16

___________ binds to the separated strands, preventing them from coming back together.

Answer 16

single-strand binding protein

Question 17

In the next step, the enzyme ___ catalyzes the synthesis of a small piece of ____ (ten to twelve nucleotides) called an RNA ___ that serves to “prime” the process of DNA replication.

Answer 17

primase
RNA
primer

Question 18

Now the enzyme _________“reads” each parental strand, also called the ____, and catalyzes the polymerization of a complementary ____ strand.

Answer 18

DNA polymerase III
template
daughter

Question 19

what are the precursors for DNA replication

Answer 19

Deoxyribonucleotide triphosphate molecules

Question 20

In this reaction, a _______group is released as a phosphoester bond is formed between the ___________ of the nucleotide being added to the chain and the ____ of the nucleotide on the daughter strand. This is called 5′ to 3′ synthesis.

Answer 20

pyrophosphate
5′-phosphoryl group
3′-OH

Question 21

Because the two strands of DNA are antiparallel and DNA polymerase can only catalyze 5′ → 3′ replication, only one of the two DNA strands (top strand) can be read continuously to produce a daughter strand. what about the other strand

Answer 21

must be synthesized in segments that are extended away from the direction of movement of the replication fork (bottom strand).
These discontinuous segments are later covalently joined together by DNA ligase.

Question 22

DNA polymerase III can only catalyze DNA chain elongation in the

Answer 22

5′ to 3′ direction

Question 23

One strand, called the ____ strand, is replicated continuously. The opposite strand, called the ____ strand, is replicated discontinuously.

Answer 23

leading

lagging

Question 24

For the leading strand, a single ____ is produced at the replication origin and ______ continuously catalyzes the addition of nucleotides in the _______, beginning with addition of the ____ nucleotide to the _____.

Answer 24

RNA primer
DNA polymerase III
5′ to 3′ direction
first 
RNA primer

Question 25

On the lagging strand, _____ are produced as the replication fork proceeds along the molecule.

Answer 25

many RNA primers

Question 26

in the lagging strand DNA polymerase III catalyzes DNA chain elongation

Answer 26

from each of these primers

Question 27

in the lagging strand When the new strand “bumps” into a previous one, synthesis

Answer 27

stops at that site

Question 28

in the lagging strand

Meanwhile, at the replication fork, a new ___is being synthesized by ____

Answer 28

primer

primase

Question 29

The final steps of synthesis on the lagging strand involve

Answer 29

removal of the primers
repair of the gaps
sealing of the fragments into an intact strand of DNA

Question 30

The enzyme DNA polymerase I catalyzes the removal of the _______ and its replacement with _____-

Answer 30

RNA primer

DNA nucleotides

Question 31

In the final step of the process, the enzyme DNA ligase catalyzes the formation of a

Answer 31

phosphoester bond between the two adjacent fragments.

Question 32

In addition to catalyzing the replication of new DNA, DNA polymerase III is able to ______________
If the wrong nucleotide has been added to the growing DNA strand, it is ___________

Answer 32

proofread the newly synthesized strand.

removed and replaced by the correct one

Question 33

Eukaryotic DNA Replication

Answer 33

DNA replication begins at many replication origins and proceeds bidirectionally along each chromosome.