Chapter 12 learning curve

____ relieves the tension on the double helix during DNA replication.

Topoisomerase

Which of the following statements is true regarding chromosome replication in eukaryotes? a. During chromosome replication, multiple origins of replication form for all DNA in a cell. b. Replication bubbles remain distinct, isolated structures during chromosome replication and never fuse with one another. c. In humans, it takes several days to replicate an entire chromosome. d. Replication begins at one end of the chromosome and proceeds until it reaches the opposite end. e. None of the answer options is correct.

a. During chromosome replication, multiple origins of replication form for all DNA in a cell.

In recombinant DNA experiments, ______ is used to cut pieces of DNA, and ______ joins these segments to form recombinant DNA. a. a restriction enzyme; DNA ligase b. a RNA polymerase; a restriction enzyme c. DNA ligase; a restriction enzyme d. a DNA polymerase; DNA ligase e. DNA ligase; a plasmid

a. a restriction enzyme; DNA ligase

Which of the following reasons explains why bacteria can continually divide? a. because their DNA is circular so the DNA never shortens after replication b. because DNA replication is much quicker in bacteria than in eukaryotes c. because they are so simple d. because they only have one chromosome e. because they have plasmids

a. because their DNA is circular so the DNA never shortens after replication

_____ requires both a template and a free 3′ end to elongate a nucleotide chain. a. Helicase b. DNA polymerase c. RNA primase d. Topoisomerase II

b. DNA polymerase

The role of dideoxynucleotides in Sanger sequencing is: a. the inhibition of restriction enzyme activity. b. the termination of DNA synthesis at specific bases. c. the removal of specific bases from DNA. d. the addition of specifically labeled phosphates to the DNA. e. the detection of protons during DNA synthesis.

b. the termination of DNA synthesis at specific bases.

All four dideoxynucleotides can be present in a single Sanger sequencing reaction and still be distinguished because: a. they are incorporated in the growing chain with different efficiency. b. they are labeled with different fluorescent dyes. c. the fragments into which they are incorporated have different mobility in a gel. d. All of these choices are correct.

b. they are labeled with different fluorescent dyes.

What is the benefit of using Taq polymerase in PCR? a. Because it is taken from bacteria that live in high temperatures, it doesn't have a proofreading function. b. Because it is taken from bacteria, this enzyme works much more efficiently than other types of DNA polymerase. c. Because it is taken from bacteria that live in high temperatures, it stays active during denaturation steps of the reaction d. Because it is taken from bacteria, it makes fewer mistakes. e. None of the answer options is correct.

c. Because it is taken from bacteria that live in high temperatures, it stays active during denaturation steps of the reaction.

Which of the following is true regarding DNA replication? a. Only the leading strand gets shortened during replication. b. Only the lagging strand gets shortened during replication. c. Both strands get shortened at opposite ends during replication. d. Both strands get shortened at the same end during replication. e. Only the lagging strand gets shortened after every other round of replication.

c. Both strands get shortened at opposite ends during replication.

What is the difference between Sanger sequencing and PCR with regard to the materials needed to perform these reactions? a. DNA polymerase is needed in Sanger sequencing but not in PCR. b. DNA polymerase is needed in PCR but not in Sanger sequencing. c. Dideoxynucleotides are needed in Sanger sequencing, but not in PCR. d. Primers are needed in PCR but not in Sanger sequencing. e. Primers are needed in Sanger sequencing but not in PCR.

c. Dideoxynucleotides are needed in Sanger sequencing, but not in PCR.

The name of the technique used to amplify specific sequences of DNA is: a. electrophoresis. b. Southern blot. c. PCR. d. hybridization. e. restriction.

c. PCR.

A Southern blot is a technique that relies on hybridization of: a. a nucleic acid probe to a complementary RNA. b. proteins to DNA. c. a nucleic acid probe to a complementary DNA. d. None of the answer options is correct.

c. a nucleic acid probe to a complementary DNA.

During PCR, where does the energy come from that adds the nucleotide to the growing DNA strand? a. the elevated temperature of the PCR reaction b. the primers c. the incoming nucleotides d. Taq polymerase e. ATP

c. the incoming nucleotides

Okazaki fragments are found on _____ strand of DNA. a. both the leading and lagging b. the parental c. the lagging d. the leading

c. the lagging

What is the function of the enzyme DNA polymerase? a. to synthesize a strand of DNA using a polypeptide as a template b. to synthesize a strand of mRNA using mRNA as a template c. to synthesize a strand of DNA using DNA as a template d. to synthesize a polypeptide using DNA as a template e. to synthesize a strand of mRNA using DNA as a template

c. to synthesize a strand of DNA using DNA as a template

Which of the following sequences is not a palindrome? a. GGATCC b. GGCGCGCC c. TTAATTAA d. ATTTAAAT e. ATTATT

d. ATTTAAAT

Failure to recover a specific band in a gel made after PCR can be attributed to: a. inappropriate annealing temperature for used primers. b. inappropriate design of primers. c. inappropriate numbers of cycles for amplification. d. All of these choices are correct.

d. All of these choices are correct.

____ moves outward from the origin of replication and breaks hydrogen bonds between DNA nucleotides. a. DNA polymerase b. RNA primase c. Topoisomerase II d. Helicase

d. Helicase

_____ is the first enzyme to synthesize a nucleic acid at a replication fork. a. Topoisomerase II b. Helicase c. DNA polymerase d. RNA primase

d. RNA primase

Which of the following statements is true regarding telomeres? a. Telomeres are typically only a few base pairs in size. b. Telomeres contain non-essential genes that are not necessary for cell survival. c. Telomeres are enzymes that repair telomerases (which cap the end of linear chromosomes). d. Telomeres can contain repeated base sequences. e. Telomeres are repaired to the same extent in germ cells and somatic cells.

d. Telomeres can contain repeated base sequences.

What would happen if telomerase stopped working in a cell in which it normally functions at high levels? a. The cells would be able to divide indefinitely. b. Cancer would be the result. c. The cell would die immediately. d. The cell would eventually die as the DNA continued to shorten. e. None of the answer options is correct.

d. The cell would eventually die as the DNA continued to shorten.

What is the name of the enzyme that separates the two strands of DNA during replication? a. primase b. DNA ligase c. DNA polymerase d. helicase e. topoisomerase

d. helicase

The following enzymes play important roles in DNA replication: DNA polymerase, primase, ligase, helicase. In what order do they work during replication? a. primase, helicase, ligase, DNA polymerase b. DNA polymerase, primase, ligase, helicase c. DNA polymerase, helicase, primase, ligase d. helicase, primase, DNA polymerase, ligase e. ligase, helicase, DNA polymerase, primase

d. helicase, primase, DNA polymerase, ligase

What is the name of the class of enzymes that recognizes and cuts a specific sequence of DNA? a. topoisomerases b. DNA polymerases c. helicases d. restriction enzymes e. primases

d. restriction enzymes

What feature is shared by restriction fragments produced by the restriction enzymes BclI (T↓GATCA) and BglII (A↓GATCT)? (The downward arrow denotes the site of cleavage in each strand.) a. Both fragments have the same 5-base overhang at the 3′-end. b. Both fragments have the same 5-base overhang at the 5′-end. c. These fragments do not have anything in common. d. Both fragments have blunt ends. e. Both fragments have the same 5-base overhang but one at the 3′-end and the other at the 5′-end.

e. Both fragments have the same 5-base overhang but one at the 3′-end and the other at the 5′-end.

Why are primers needed for DNA replication? a. A tiny amount of RNA is needed to tell the cell where genes are located. b. The primers help with the proofreading function of DNA polymerase. c. They help with the joining of Okazaki fragments. d. They help direct the placement of the telomeres. e. DNA polymerase can only add nucleotides to an existing chain.

e. DNA polymerase can only add nucleotides to an existing chain.

Which of the following statements is true regarding origins of replication? a. Circular DNA always has between 2 and 3 origins of replication. b. Eukaryotic DNA always has one origin of replication. c. The replication bubbles associated with different origins of replication never fuse. d. Origins of replication are synonymous with replication forks. e. None of the answer options is correct.

e. None of the answer options is correct.

The point at which DNA synthesis is initiated is called the: a. primase. b. primer. c. replication fork. d. start codon. e. origin of replication.

e. origin of replication.

During DNA replication, the leading strand contains Okazaki fragments. T or F?

false

If a restriction site of AatII is 5′-GACGTC -3′ then 3′-GACGTC-5′ is also an AatII restriction site. T or F?

false

In gel electrophoresis, DNA fragments migrate toward the negative pole of the electric field. T or F?

false

Okazaki fragments are ligated into a continuous DNA molecule after replication is completed. T or F?

false

The first step of PCR is called annealing. T or F?

false

A transgenic organism is synonymous with a genetically modified organism, as both can contain recombinant DNA. T or F?

true

In circular DNA, the DNA molecule is not shortened during replication. T or F?

true

Synthesis of nucleic acids always occurs in the 5′ → 3′ direction. T or F?

true