Ch. 3 End Of Chapter Questions

Question 1

Which of the following statemenrs about DNA isolation from E. coli is not correct?

Answer 1

Detergent is used to break apart plant cells to extract DNA

Question 2

Which of the following statements is important for gel electrophoresis to work?

Answer 2

All of the above

• negatively charged nucleic acids to migrate through the gel
• ethidium bromide to provide a means to visualize the DNA in the gel
• agarose or polyacrylamide to separate the DNA based on size
• known molecular weight standards

Question 3

How are restriction enzymes and ligase used in biotechnology?

Answer 3

Restriction enzymes cut DNA at specific locations, producing ends that can be ligated back together with ligase

Question 4

Which of the following is an appropriate method for detecting nucleic acids?

Answer 4

All of the above

• measuring absorbance at 260nm
• autoradiography of radiolabeled nucleic acids
• chemiluminescence of DNA labeled with biotin or digoxigenin
• measuring the light emitted after excitation by fluorescent-labeled nucleic acids on a photodetector

Question 5

Why does the GC content of a particular DNA molecule affect the melting of the two strands?

Answer 5

Because G and C base-pairing requires theee hydrogen bonds and a higher temperature is required to “melt” the DNA

Question 6

What is the different between southern and northern hybridizations?

Answer 6

Southern blots hybridize a DNA probe to a digested DNA sample but northern blots hybridize a DNA probe to, usually, mRNA

Question 7

What might be a use for fluorescence in situ hybridization? (FISH)

Answer 7

For identification of a specific gene by hybridization to a DNA probe within live cells that have had their DNA denatured by heat

Question 8

Which of the following are useful traits of cloning vectors?

Answer 8

All of the above

• an antibiotic resistance gene on the plasmid for selection of cells containing the plasmid
• a site that contains unique, clustered restriction enzyme sequences for cloning foreign DNA
• a high copy number plasmid so that large amounts of DNA can be obtained
• alpha complementation to determine if the foreign DNA was inserted into the cloning site

Question 9

Which of the following vectors holds the largest pieces of DNA?

Answer 9

PACs

Question 10

Besides a high voltage shock, what is another method to make E. coli competent to take up “naked” DNA?

Answer 10

High concentrations of calcium ions followed by high temperature

Question 11

Why are gene libraries constructed?

Answer 11

All of the above

• to find new genes
• to sequence whole genomes
• to compare genes to other organisms
• to create a “bank” of all the genes in an organism

Question 12

Which of the following statements about gene libraries is correct?

Answer 12

Genes in a library can be compared to genes from other organisms by hybridization with a probe

Question 13

Why must reverse transcriptase be used to create a eukaryotic expression library?

Answer 13

Reverse transcriptase creates cDNA from mRNA because genes in eukaryotes have large numbers of non-coding regions

Question 14

Which of the following are common features of expression vectors?

Answer 14

All of the above

• small segments of DNA that encode tags for protein purification
• transcriptional start and stop sites
• a tightly controlled promoter that can only be induced under certain circumstances
• antibiotic resistance gene

Question 15

Which method is used to construct large, recombinant vectors when polylinker restriction enzymes are not useful?

Answer 15

Recombineering

Question 16

Which statement about Gateway cloning is not true?

Answer 16

The ccdB gene produces a toxin within host cells carrying the gene of interest.