Genetics Test 2 Chapter 11

DNA Polymerase I

composed of a single polypeptide; Removes RNA primers, fills in gaps with DNA

Two newly made DNA strands

daughter strands

Semiconservative model

double stranded DNA contains one parental and one daughter strand following replication

GATC methylation sites .....

ensure only one round of replication

catenanes

intertwined circular molecules are termed. seperated by topoisomerase

Leading strand

one RNA primer made at the origin

Origin of replication in E.Coli

oriC

Dispersive model

parental and daughter DNA segments are interspersed in both strands following replication

Two original DNA strands

parental strands

DNA Replication

process by which the genetic material is copied

Telomere

refers to the complex of telomeric DNA sequences and bound proteins

There are two ___________ ___________ that eventually meet at the opposite end of the bacterial chromosome

replication forks

Watson and Cricks work proved that DNA replication is ___________________.

semiconservative

DNA Helicase

seperates the DNA in the 5' - 3' direction using ATP and by breaking the hydrogen bonds, on both strands

Okazaki fragments

small DNA fragments on lagging strand

Primase

synthesized small 10 to 12 nucleotide RNA primers

Ter

termination sequences, T1 stops counterclockwise forks, T2 stops clockwise forks

function of topoisomerase II, or DNA gyrase

travels ahead of helicase and alleviates supercoils

Temperature-sensitive mutant

ts mutant can survive at the permissive temperature, but will fail to grow at the non permissive temperature

15. How many origins of replication are found in a prokaryotic cell? A) 1 B) 10 C) dozens D) thousands

A) 1

24. _____ removes the RNA nucleotides of the primers and replaces them with DNA nucleotides. A) DNA polymerase I B) single-strand binding protein C) helicase D) topoisomerase E) DNA polymerase III

A) DNA polymerase I

6. The enzyme known as _________ uses __________ and separates the DNA strands at the replication fork. A) helicase, ATP B) helicase, GTP C) gyrase, ATP D) gyrase, GTP

A) helicase, ATP

8. DNA polymerase III is a processive enzyme, which means that A) it does not dissociate from the growing strand during DNA synthesis. B) it makes a new strand very quickly. C) It proceeds toward the opening of the replication fork. D) It copies DNA with relatively few errors.

A) it does not dissociate from the growing strand during DNA synthesis.

11. To synthesize new DNA strands, DNA polymerase III requires ________ as template. A) single-stranded DNA B) double-stranded DNA C) single-stranded RNA D) double-stranded RNA

A) single-stranded DNA

Three types of DNA sequences that are important in oriC.

AT-rich region, DnaA boxes, GATC methylation sites

4. A site in a chromosome where DNA replication begins is A) A promoter. B) An origin of replication. C) An operator. D) A replication fork.

B) An origin of replication.

3. The model that correctly describes the process of DNA replication is A) the conservative model. B) The semi-conservative model. C) The dispersive model. D) All of the above.

B) The semi-conservative model.

14. Okazaki fragments are involved in the synthesis of _______. A) the leading strand only B) the lagging strand only C) both the leading strand and the lagging strand D) the leading strand in prokaryotes, the lagging strand in eukaryotes.

B) the lagging strand only

10. DNA replication is initiated from _______. A) single-stranded DNA primers B) double-stranded DNA primers C) single-stranded RNA primers D) double-stranded RNA primers

C) single-stranded RNA primers

DNA Ligase

Covalently attaches adjacent okazaki fragments; catalyzes the formation of a phosphodiester bond

5. The origin of replication in E. coli contains A) an AT-rich region. B) DnaA box sequences. C) GATC methylation sites. D) All of the above.

D) All of the above.

9. To synthesize DNA, what does telomerase use as a template? A) It uses the DNA in the 3' overhang. B) It uses RNA that is a component of telomerase. C) No template is used. D) Both A) and B) are correct

D) Both A) and B) are correct It uses the DNA in the 3' overhang. It uses RNA that is a component of telomerase.

7. In the lagging strand, DNA is made in the direction ____________ the replication fork and is made as _______. A) toward, one continuous strand B) away from, one continuous strand C) toward, Okazaki fragments D) away from, Okazaki fragments

D) away from, Okazaki fragments

2. To make a new DNA strand, which of the following is necessary? A) a template strand. B) nucleotides. C) heavy nitrogen. D) both A) and B).

D) both A) and B) a template strand, nucleotides.

12. DNA ligase forms ________ between adjacent nucleotides. A) peptide bonds B) ionic bonds C) hydrogen bonds D) phosphodiester bonds

D) phosphodiester bonds

16. How many origins of replication are found in a eukaryotic cell? A) 1 B) 10 C) dozens D) thousands

D) thousands

23. _____ reduces DNA supercoiling and torsional stress that is created ahead of the replication fork. A) DNA polymerase I B) single-strand binding protein C) helicase D) topoisomerase E) DNA polymerase III

D) topoisomerase

primosome

DNA helicase and primase are physically bound to each other to form a complex called ________.

Fidelity

DNA replication exhibits a high degree of fidelity; mistakes are extremely rare.

Origin of replication

DNA synthesis begins at this site

19. Suppose that some cells are grown in culture in the presence of radioactive nucleotides for many generations, so that both strands of every DNA molecule are radioactive. The cells are then harvested and placed in new medium with nucleotides that are not radioactive, so that newly synthesized DNA will not be radioactive. What proportion of DNA molecules will be radioactive after two rounds of replication? A) none B) 1/8 C) 1/4 D) 1/3 4 E) 1/2

E) 1/2

25. _____ prevents the separated DNA strands from rewinding into a double helix.A) DNA polymerase I B) single-strand binding protein C) helicase D) topoisomerase E) DNA polymerase III

E) DNA polymerase III

True or False 2. All eukaryotic cells undergo DNA replication.

False

True or False 3. DNA nucleotides carry -OH on the 1' carbon.

False

True or False 4. DNA nucleotides carry -OH on the 2' carbon

False

Lagging strand

Synthesis in the 5' to 3' direction, many RNA primers necessary

DNA Polymerase III enzymes are responsible for ......

Synthesizing the DNA; composed of 10 subunits

The splitting of the DNA double helix results in two __________.

Template strands

Single stranded binding proteins

binds to seperated DNA strands to keep them apart.

Conservative model suggested :

both parental strands stay together after DNA replication

26. What is semiconservative replication?

26. In semiconservative replication, the original two strands of the DNA double helix serve as templates for new strands of DNA. When replication is complete, two double-stranded DNA molecules will be present. Each will consist of one original template strand and one newly synthesized strand that is complementary to the template.

22. _____ unwinds the double helix by breaking hydrogen bonds between the two strands at the replication fork. A) DNA polymerase I B) single-strand binding protein C) helicase D) topoisomerase E) DNA polymerase III

C) helicase

27. List the different proteins and/or enzymes taking part in bacterial DNA replication. Give the function of each in the bacterial DNA replication process (know at least five proteins and/or enzymes).

27. DNA polymerase III is the primary DNA replication enzyme involved. It elongates a new DNA strand from the 3' end of the primer. DNA polymerase I removes the RNA nucleotides of the RNA primers and replaces them with DNA nucleotides. DNA ligase connects Okazaki fragments by sealing nicks in the sugar-phosphate backbone. Primase synthesizes the RNA primers that provide the 3'-OH group needed for DNA polymerase III to initiate DNA synthesis. DNA helicase unwinds the DNA double helix by breaking hydrogen bonds between the two strands at the replication fork. DNA gyrase reduces DNA supercoiling and torsional strain that is created ahead of the replication fork by making double-stranded breaks in the DNA and resealing it. Gyrase is also called topoisomerase II. DnaA proteins bind to the replication origin and unwind short regions of DNA. Single-strand binding protein (SSB protein) stabilizes single-stranded DNA prior to replication by binding to it, thus preventing the DNA from rewinding with its complementary sequences.

Synthesis of DNA proceeds ________________.

Bidirectionally

Tus

Binds to ter sequences and prevents the advancement of the replication fork

13. DNA polymerase always synthesizes new DNA by adding nucleotides onto the previous ______. A) 3' phosphate group 3 B) 5' phosphate group C) 3' hydroxyl group D) 5' hydroxyl group

C) 3' hydroxyl group

17. Where are primers found on the lagging strand during DNA synthesis? A) Only at the 5' end of the newly synthesized lagging strand. B) Only at the 3' end of the newly synthesized lagging strand. C) At the beginning of every Okazaki fragment. D) At the end of every Okazaki fragment.

C) At the beginning of every Okazaki fragment.

Refer to study guide for 20

C) C

Refer to study guide for 21

C) C

18. What would happen if an organism's telomerase were non-functional? A) No DNA replication would take place. B) The DNA polymerase would stall at the telomere. C) Chromosomes would shorten with each round of cell division. D) RNA primers could not be removed.

C) Chromosomes would shorten with each round of cell division.

1. The complementarity of DNA strands is based on A) the chemical properties of a phosphodiester linkage. B) The binding of proteins to the DNA. C) The AT/GC rule. D) All of the above.

C) The AT/GC rule.

True or False 5. DNA nucleotides carry -OH on the 3' carbon.

True

True or False 1. DNA replication occurs in a semi-conservative manner

True; Only most not all