Question 1

What supplies the energy that drives the relief of mechanical strain by DNA gyrase?

Accepted Answer

DNA gyrase relieves mechanical strain in DNA strands during processes such as replication and transcription by introducing negative supercoils into DNA. This process is powered by the hydrolysis of ATP, not by condensation reactions, GTP hydrolysis, or a proton gradient.

Question 2

Bacteria are grown in a medium containing ¹⁵NH₄Cl for a number of generations so that all of the DNA is made of fully "heavy" DNA.The bacteria are moved to a new medium and grown in ¹⁴NH₄Cl so that all new DNA will be "light".If replication were dispersive,what would the DNA look like after two generation times.

Accepted Answer

D

Question 3

Why is a single-stranded,circular DNA an ineffective template for DNA polymerase?

Accepted Answer

DNA polymerase requires a 3'-hydroxyl group on the template strand to add nucleotides to the growing strand. In a single-stranded, circular DNA, there is a template strand but no 3'-hydroxyl group available for DNA polymerase to add the nucleotides. Hence, it is an ineffective template for DNA polymerase.

Question 4

The specific site on the bacterial chromosome at which replication begins is called the ________.

Accepted Answer

The origin is the specific site on the bacterial chromosome at which replication begins.

Question 5

In early experiments with DNA polymerase I,what evidence convinced investigators that the original unlabeled DNA in the reaction mixture served as the template for the newly made DNA?

Accepted Answer

If the new DNA had the same base composition as the original unlabeled DNA, it suggests that the original DNA served as the template for the newly made DNA. This is because DNA polymerase adds complementary nucleotides to the template strand, resulting in a new strand that has the same base composition as the original strand. The other options (B, C, D, and E) are not supported by the evidence and do not relate to the use of original template DNA.

Question 6

What type of replication results in the integrity of both parental strands being disrupted? The new duplex strands are made of both old and new DNA.Neither the parental strands nor the parental duplex is preserved.

Accepted Answer

Dispersive replication results in the disruption of both parental strands and the formation of new duplex strands made of both old and new DNA. Neither the parental strands nor the parental duplex is preserved. This type of replication was proposed by Max Delbrück and reported in 1958.

Question 7

What happens to DNA (circular DNA or linear DNA that is not free to rotate)when it becomes overwound?

Accepted Answer

When DNA becomes overwound, it becomes positively supercoiled. This occurs because the overwinding of the DNA causes the double helix to twist in the opposite direction, which results in the DNA becoming more tightly coiled. This can occur in circular DNA or in linear DNA that is not free to rotate.

Question 8

Replication moves outward from the origin in ________ direction(s)and is said to be ________.

Accepted Answer

The answer of Replication moves outward from the origin in...

Question 9

Where is DNA gyrase normally positioned as it changes positively supercoiled DNA into negatively supercoiled DNA in the replicating circular,bacterial chromosome?

Accepted Answer

DNA gyrase travels along the DNA ahead of the replication fork, relieving the torsional stress caused by the unwinding of the double helix. This allows for the DNA to be negatively supercoiled, which facilitates further replication.

Question 10

Who was the first to suggest semiconservative replication?

Accepted Answer

Watson and Crick first suggested the mechanism of semiconservative replication when they proposed the double helix structure of DNA. They theorized that each strand of the DNA molecule could serve as a template for the production of a new, complementary strand.

Question 11

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU),which replaces thymidine in DNA.After two rounds of replication,what does the DNA look like?

Accepted Answer

After two rounds of replication, the original strand with thymidine (T) would have been replicated and replaced with BrdU. Thus, one chromatid will have both strands with BrdU (from the original strand and the newly synthesized strand), while the other chromatid will have one strand with BrdU (from the newly synthesized strand) and one strand with T (from the original strand). This results in half of the chromatids having two strands that contain BrdU and half of the chromatids having one strand lacking BrdU and one strand containing BrdU.

Question 12

Who was the first to purify an enzyme from bacterial extracts that could incorporate DNA precursors into a polymer?

Accepted Answer

Arthur Kornberg was the first to purify an enzyme from bacterial extracts that could incorporate DNA precursors into a polymer. This enzyme was called DNA polymerase. James Watson and Francis Crick are known for discovering the structure of DNA, while Jacques Monod was a French biochemist who worked on the lac operon. There is no record of Joel B. Piperberg making any significant contributions to the field of enzymology.

Question 13

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU),which replaces thymidine in DNA.After one round of replication,what does the DNA look like?

Accepted Answer

The answer of Cultured mammalian cells grown in thymidine for...

Question 14

Which type of replication results in 2 duplexes made of one parental strand and one newly synthesized strand?

Accepted Answer

Semiconservative replication results in two strands of DNA, each made up of one parental strand and one newly synthesized strand. This is supported by the experiment by Meselson and Stahl in 1958, where they labeled the parent DNA with a heavier isotope of nitrogen and then observed the resulting DNA after replication with a lighter isotope of nitrogen. The resulting DNA showed one heavy strand and one light strand, supporting the theory of semiconservative replication. Conservative replication would result in two duplexes, one entirely made up of the parent DNA and one entirely made up of the newly synthesized DNA, which is not observed in most cases. Dispersion replication would result in fragments of the parent and the newly synthesized DNA in each duplex, and incisive and reservative replication are not valid terms in describing DNA replication.

Question 15

Why is an intact,linear double helix an ineffective template for DNA polymerase?

Accepted Answer

The answer of Why is an intact,linear double helix an...

Question 16

The replication fork generates _______ supercoils in the _______ portion of the DNA molecule.

Accepted Answer

The replication fork generates positive supercoils in the unreplicated portion of the DNA molecule due to the unwinding of the double helix ahead of the replication machinery.

Question 17

Bacteria are grown in a medium containing ¹⁵NH₄Cl for a number of generations so that all of the DNA is made of fully "heavy" DNA.The bacteria are moved to a new medium and grown in ¹⁵NH₄Cl so that all new DNA will be "light".If replication were conservative,what would the DNA look like after two generation times.

Accepted Answer

The answer of Bacteria are grown in a medium containing...

Question 18

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU),which replaces thymidine in DNA.After one round of replication,what would the DNA look like if replication were dispersive?

Accepted Answer

The answer of Cultured mammalian cells grown in thymidine for...

Question 19

In replicating bacterial chromosomes,where does replication terminate?

Accepted Answer

Replication of bacterial chromosomes starts at a single origin and proceeds in both directions around the circular chromosome until it meets at the opposite side of the origin. Therefore, replication terminates across the circular chromosome from the origin.

Question 20

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU),which replaces thymidine in DNA.After two rounds of replication,what would the DNA look like if replication were conservative?

Accepted Answer

The answer of Cultured mammalian cells grown in thymidine for...

Quiz 13: Dna Replication and Repair

What supplies the energy that drives the relief of mechanical strain by DNA gyrase?

Why is a single-stranded,circular DNA an ineffective template for DNA polymerase?

The specific site on the bacterial chromosome at which replication begins is called the ________.

In early experiments with DNA polymerase I,what evidence convinced investigators that the original unlabeled DNA in the reaction mixture served as the template for the newly made DNA?

What type of replication results in the integrity of both parental strands being disrupted? The new duplex strands are made of both old and new DNA.Neither the parental strands nor the parental duplex is preserved.

What happens to DNA (circular DNA or linear DNA that is not free to rotate) when it becomes overwound?

Replication moves outward from the origin in direction(s) and is said to be .

Where is DNA gyrase normally positioned as it changes positively supercoiled DNA into negatively supercoiled DNA in the replicating circular,bacterial chromosome?

Who was the first to suggest semiconservative replication?

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU) ,which replaces thymidine in DNA.After two rounds of replication,what does the DNA look like?

Who was the first to purify an enzyme from bacterial extracts that could incorporate DNA precursors into a polymer?

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU) ,which replaces thymidine in DNA.After one round of replication,what does the DNA look like?

Which type of replication results in 2 duplexes made of one parental strand and one newly synthesized strand?

Why is an intact,linear double helix an ineffective template for DNA polymerase?

The replication fork generates _ supercoils in the _ portion of the DNA molecule.

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU) ,which replaces thymidine in DNA.After one round of replication,what would the DNA look like if replication were dispersive?

In replicating bacterial chromosomes,where does replication terminate?

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU) ,which replaces thymidine in DNA.After two rounds of replication,what would the DNA look like if replication were conservative?

Quiz 13: Dna Replication and Repair

What supplies the energy that drives the relief of mechanical strain by DNA gyrase?

Why is a single-stranded,circular DNA an ineffective template for DNA polymerase?

The specific site on the bacterial chromosome at which replication begins is called the ________.

In early experiments with DNA polymerase I,what evidence convinced investigators that the original unlabeled DNA in the reaction mixture served as the template for the newly made DNA?

What type of replication results in the integrity of both parental strands being disrupted? The new duplex strands are made of both old and new DNA.Neither the parental strands nor the parental duplex is preserved.

What happens to DNA (circular DNA or linear DNA that is not free to rotate) when it becomes overwound?

Replication moves outward from the origin in ________ direction(s) and is said to be ________.

Where is DNA gyrase normally positioned as it changes positively supercoiled DNA into negatively supercoiled DNA in the replicating circular,bacterial chromosome?

Who was the first to suggest semiconservative replication?

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU) ,which replaces thymidine in DNA.After two rounds of replication,what does the DNA look like?

Who was the first to purify an enzyme from bacterial extracts that could incorporate DNA precursors into a polymer?

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU) ,which replaces thymidine in DNA.After one round of replication,what does the DNA look like?

Which type of replication results in 2 duplexes made of one parental strand and one newly synthesized strand?

Why is an intact,linear double helix an ineffective template for DNA polymerase?

The replication fork generates _______ supercoils in the _______ portion of the DNA molecule.

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU) ,which replaces thymidine in DNA.After one round of replication,what would the DNA look like if replication were dispersive?

In replicating bacterial chromosomes,where does replication terminate?

Cultured mammalian cells grown in thymidine for many generations were allowed to undergo replication in the presence of bromodeoxyuridine (BrdU) ,which replaces thymidine in DNA.After two rounds of replication,what would the DNA look like if replication were conservative?

Replication moves outward from the origin in direction(s) and is said to be .

The replication fork generates _ supercoils in the _ portion of the DNA molecule.