GENETICS CH 12

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 include radioactive nucleotides. The cells are then harvested and placed in new Moderate with nucleotides that are not radioactive so that newly synthesized DNA will not be radioactive. What proportion of DNA molecules will contain radioactivity after two rounds of replication?

1/2

You are studying a new virus with a DNA genome of 12 Kb. It can synthesize DNA at a rate of 400 nucleotides per second. If the virus uses theta replication, how long will it take to replicate its genome?

15 seconds

The nuclear genome of a single human cell (i.e., the entire diploid complement) contains about 6.6 billion (6.6 × 10 9) base pairs of DNA. If synthesis at each replication fork occurs at an average rate of 50 nucleotides per second, all the DNA is replicated in 5 minutes. Assume that replication is initiated simultaneously at all origins. Reference: Ref 12-1 How many origins of replication exist in a human diploid genome?

220,000

You are studying a new virus with a DNA genome of 12 Kb. It can synthesize DNA at a rate of 400 nucleotides per second. If the virus uses rolling-circle replication, how long will it take to replicate its genome?

30 seconds

All DNA polymerases synthesize new DNA by adding nucleotides to the _____ of the growing DNA chain.

3′ OH

DNA polymerases require all of the following for DNA replication EXCEPT:

3′ to 5′ polymerase activity.

The proofreading function of DNA polymerases involves _____ activity.

3′ → 5′ exonuclease

DNA polymerase I and DNA polymerase III both have _____ activity but only DNA polymerase I has _____ activity.

3′ → 5′ exonuclease; 5′ → 3′ exonuclease

The nuclear genome of a single human cell (i.e., the entire diploid complement) contains about 6.6 billion (6.6 × 10 9) base pairs of DNA. If synthesis at each replication fork occurs at an average rate of 50 nucleotides per second, all the DNA is replicated in 5 minutes. Assume that replication is initiated simultaneously at all origins. Reference: Ref 12-1 Assuming that the origins are approximately equally distributed across the chromosomes, what is the average number of origins per human chromosome?

4783

Use the figure below the answer the following questions.

A and D

The diagram shown below is one half of a replication bubble. As the DNA template strands unwind towards the right, new strands of DNA get synthesized. Which of the following represents a lagging strand?

B

In the diagram below, which letter indicates the 5′ end of the leading strand?

C

Use the figure below the answer the following questions.

C and F

Use the figure below the answer the following questions.

D and E

Which of the following enzyme and function pairs is INCORRECTLY matched?

DNA helicase; rewinding and reforming the DNA double helix as the replication terminates

DNA primase requires a _____ template and _____ nucleotides to initiate primer synthesis.

DNA;RNA

Which statement CORRECTLY describes why the DNA synthesis is discontinuous on one template strand while continuous on the other? (Select all that apply.)

It is due to the nature of the DNA polymerase which can only add new nucleotide at the 3ʹ end. AND It is due to antiparallel nature of the DNA molecule.

DNA synthesis during replication is initiated from:

RNA primers

If ribonucleotides were depleted from a cell during S phase, how would DNA synthesis be affected? (Ignore energetic considerations.)

Replication would cease because ribonucleotides are required to initiate DNA synthesis.

If a deletion occurs in a gene that encodes DNA polymerase I and no functional DNA polymerase I is produced, what will be the MOST likely consequence of this mutation?

The DNA strands would contain pieces of RNA

Which one of the following statements is NOT true for all E. coli DNA polymerases?

They possess 5′ → 3′ exonuclease activity.

Which of the following is a protein that facilitates the termination of replication in E. coli?

Tus

Okazaki fragments are found in all of the following EXCEPT in:

the leading strand.

Which of the following eukaryotic DNA polymerases and their role is INCORRECTLY paired?

ε (epsilon); translesion DNA synthesis

Which activity is NOT associated with DNA polymerases?

ability to synthesize a DNA from scratch without a primer

Telomerase uses _____ to synthesize new DNA

an RNA template

During DNA replication, the synthesis of the new strand requires the addition of a new dNTP to the 3ʹ-OH group of the growing nucleotide strand by DNA polymerase. Which of the following provides the energy needed for this step?

cleavage of two phosphate groups from the dNTP

What is the function of DNA ligase?

connects Okazaki fragments by sealing nicks in the sugar-phosphate backbone

What type of synthesis occurs on the leading strand?

continuous

You learn that a Mars lander has retrieved a bacterial sample from the polar ice caps. You obtain a sample of these bacteria and perform the same kind of experiment that Meselson and Stahl did to determine how the Mars bacteria replicate their DNA. Based on the following equilibrium density gradient centrifugation results, what type of replication would you propose for these new bacteria?

dispersive

Telomerase activity is MOST likely to be found in which cells in humans?

germ line

For which of the following is the "end-replication problem" relevant?

linear chromosomes

What type of bonds does DNA ligase create between adjacent nucleotides?

phosphodiester

What is the function of single-strand-binding proteins?

prevent the formation of secondary structures within single-stranded DNA

Which of the following enzymes do NOT aid in the unwinding of DNA for replication?

primase

Which of the following typically only have one origin of replication?

prokaryotes

What is the function of DNA gyrase?

reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding

Which of the following does NOT utilize bidirectional replication?

rolling circle model

Suppose Meselson and Stahl had obtained the following results in their experiment. These results would be consistent with which model of replication?

semiconservative and dispersive replication

Meselson and Stahl showed that DNA is replicated by a:

semiconservative system.