Deck 13: Bacterial Genetics

Question 1

Restriction enzymes were named because they restrict

A) the capacity for viral growth.
B) the growth of the bacteria that produces them.
C) bacterial translation.
D) bacterial transformation.
E) bacterial transcription.

Answer 1

A

Question 2

If DNA had 5 different bases,a restriction enzyme with a 4-base recognition sequence would cut DNA approximately every

A) 125 bp.
B) 256 bp.
C) 425 bp.
D) 625 bp.
E) 1056 bp.

Answer 2

D

Question 3

Which of the following is an example of a recombinant DNA molecule?

A) a PCR-amplified fragment
B) a single-stranded RNA hybridized to a single-stranded DNA
C) a genomic fragment of human DNA ligated to a bacterial plasmid vector
D) a chromosome in a bacterial cell
E) a bacterial plasmid cut with a restriction enzyme

Answer 3

C

Question 4

PCR cannot be successfully performed without

A) at least 100 starting DNA molecules.
B) at least some sequence information about the region to be amplified.
C) a cDNA version of the region to be amplified.
D) a section of at least 100 kb to amplify.
E) an undamaged,nondegraded DNA sample.

Question 5

In gel electrophoresis of DNA,fragments move at different rates because they have different

A) charge densities.
B) sizes.
C) base sequences.
D) amino acid compositions.
E) electrical strengths.

Question 6

The following image shows the products from Sanger sequencing.If a primer for PCR is designed to hybridize to the template,what will be its last four bases be (5' to 3',left to right)?

A) GCGA
B) CTGG
C) CCGA
D) CGCT
E) TCGC

Question 7

Which of the following would not have its gene represented in a cDNA library from red blood cell precursors if the library was made by selected polyadenylated transcripts?

A) a globin
B) a glycolysis enzyme
C) a ribosomal protein
D) a tRNA
E) an RNA polymerase

Question 8

What charge does DNA have,and what gives it this charge?

A) positive;phosphates
B) positive;bases
C) negative;phosphates
D) negative;bases
E) negative;ribose

Question 9

A plasmid has tet^r and lacZ genes for tetracycline resistance and ß-galactosidase,respectively.There is a single EcoRI site within lacZ,and a single HindIII site within tet^r.The EcoRI-HindIII cut plasmid is combined with a DNA fragment with compatible ends.Cells that contain the plasmid with the insert will be

A) tetracycline resistant and blue if grown on X-gal.
B) tetracycline sensitive and blue if grown on X-gal.
C) tetracycline resistant and white if grown on X-gal.
D) tetracycline sensitive and white if grown on X-gal.
E) X-gal resistant and blue if grown on tetracycline.

Question 10

In Sanger sequencing,what causes DNA synthesis to terminate at a specific base?

A) chemicals that cleave DNA after particular bases
B) fluorescent chemicals
C) nucleotide triphosphates that lack a base
D) nucleotide triphosphates that lack a hydroxyl
E) nucleosides that lack a 5' phosphate

Question 11

The following image shows the products from Sanger sequencing.What is the sequence of the template strand (5' to 3' left to right)?

A) GACCGCT
B) TCGCCAG
C) AGCGGTC
D) CTGGCGA
E) GGATCCC

Question 12

What is the reason for partial digestion of genomic DNA with restriction enzymes?

A) generating blunt ends,when only enzymes that leave sticky ends are available
B) generating sticky ends,when only enzymes that leave blunt ends are available
C) cutting only one strand of a restriction site,leaving a nick instead of a break
D) producing fragments that are slightly shorter than a complete digest would produce
E) producing fragments that are slightly longer than a complete digest would produce

Question 13

What information cannot be determined from the DNA sequence of a cDNA clone?

A) exon sequences
B) sequence of the promoter
C) similarity to previously identified sequences
D) amino acid sequence of the encodedpolypeptides
E) sequence of the spliced mRNA transcript

Question 14

PCR is used to

A) generate DNA fragments for genomic libraries.
B) generate DNA fragments for cDNA libraries.
C) determine the sequence of a DNA fragment by the Maxam-Gilbert procedure.
D) amplify minute quantities of a DNA fragment.
E) replicate recombinant plasmids.

Question 15

Genomic DNA is isolated from bacteria.After a long digestion with a 6-base cutting enzyme that recognizes the sequence GAATTC,the DNA is not cut.The genome is 4 Mb,so there should be approximately 1,000 sites in the DNA.What is the most likely explanation?

A) There are no Gs in the genome.
B) There are no As in the genome.
C) The bacterium methylated the DNA,because it produces the 6-base cutting enzyme.
D) All the recognition sites are in genes,and the enzyme will not cut in genes.
E) All the recognition sites are in promoters and regulatory sequences,and the enzyme cuts only in genes.

Question 16

A genomic library is a

A) collection of DNA fragments from an organism,inserted into vectors.
B) collection of restriction enzymes that make regularly spaced cuts in a genome.
C) series of DNA fragments generated by chemical cleavage,used to determine sequence.
D) set of genes that can be inserted into vectors to confer antibiotic resistance.
E) collection of mRNA molecules cloned into vectors.

Question 17

Two DNA fragments are separated by electrophoresis.How is the fragment that traveled farther different from the other fragment?

A) It is longer.
B) It is shorter.
C) It is more negatively charged.
D) It has blunt ends.
E) It has sticky ends.

Question 18

The lacZ gene is sometimes included in a cloning vector.What does it encode?

A) a restriction enzyme that cuts the vector while it is in transformed cells
B) a blue pigment that identifies any cell that has beentransformed
C) an enzyme that converts RNA to DNA
D) an enzyme that confers antibiotic resistance
E) a detectable enzyme that is not produced if the gene is interrupted by an insert

Question 19

Which of the following would be found in a cDNA library,but not a genomic library?

A) centromeres
B) replication origins
C) promoters
D) exons
E) introns

Question 20

One of the reasons that PCR is useful in diagnosis of HIV is because it

A) detects antibodies against the virus.
B) interferes with viral replication,causing the virus to become latent.
C) automatically determines the sequence,as well as the presence of the viral genome.
D) detects an infection at an earlier stage than the current standard test.
E) detects both viral DNA and viral proteins.

Question 21

A 16 kb linear DNA is cut with EcoRI and BamHI.The EcoRI digest yields fragments of 2,6,and 8 kb.The BamHI digest yields fragments of 5 and 11 kb.An EcoRI-BamHI double digest yields 2,3,5,and 6 kb fragments.If the 3 kb fragment from the double digest is used as the probe in a Southern blot of the EcoRI digest,to which fragment(s)will it hybridize?

A) 2 kb
B) 6 kb
C) 8 kb
D) 2 and 6 kb
E) 6 and 8 kb

Question 22

A 6-base cutting enzyme should cut every 4 kb,on average.Approximately how many sites are in the human genome (for simplicity,use 4 million kb as the size of the human genome)?

A) 100
B) 1,000
C) 10,000
D) 100,000
E) 1,000,000

Question 23

Ifa single DNA molecule is amplified by PCR,how many DNA molecules will there be after six cycles?

A) 6
B) 12
C) 24
D) 64
E) 86

Question 24

If the restriction enyzme EcoRI cuts a linear 19 kb piece of DNA into fragments of 1,3,6,and 9 kb,what size fragment (in kb)would not be possible from a partial digest?

A) 12
B) 10
C) 7
D) 5
E) 4

Question 25

Which mutation in the β-globin gene could,in theory,be detected with a genomic clone but not with a cDNA clone?

A) a point mutation that changes a single amino acid
B) a mutation that prevents removal of one intron
C) a promoter mutation that prevents transcription
D) a 10 bp deletion in an exon
E) a frameshift mutation

Question 26

Which statements are true?
I)In thalassemia,globin proteins are produced,but contain a point mutation.
Ii)In sickle-cell anaemia,globin proteins are produced,but contain a point mutation.
Iii)Sickle-cell anaemia is caused by a mutation in the β-globin gene.
Iv)Sickle cell anaemia is caused by a mutation in the α-globin gene.

A) i,ii
B) i,iii
C) ii,iii
D) i,iv
E) ii,iv

Question 27

Pseudogenes are evidence for

A) gene duplications.
B) the existence of integrated viruses,or proviruses.
C) the importance of TATA boxes in eukaryotic promoters.
D) the importance of the order of the globin genes in dictating their expression.
E) diseases that result from deletions in the α-globin genes.

Question 28

A restriction enzyme with a recognition site of 10 bp cuts an average of every

A) 4¹⁰ bp.
B) 10⁴ bp.
C) 2¹⁰ bp.
D) 10² bp.
E) 2⁴ bp.

Question 29

Where do restriction enzymes come from,and what is their normal physiological function?

A) Phage produces them and they replicate viral DNA.
B) Phage produces them and they confer antibiotic resistance.
C) They are yeast DNA replication enzymes.
D) Bacteria produce them to protect against viral invasion.
E) They are bacterial DNA replication enzymes.

Question 30

How do bacteria protect their own DNA from the restriction enzymes they produce?

A) Their DNA never contains the recognitionsite.
B) Ligase connects their DNA as soon as it is cut.
C) Digestion is blocked by methyl groups added to recognition sequences in their DNA.
D) Phosphate groups added to the recognition sequences in their DNA block digestion.
E) Restriction enzymes are blocked from entry into the nucleus.

Question 31

How are the genes in the beta-globin locus different from each other?

A) They use different template strands for transcription.
B) They are expressed at different times in development.
C) They have different evolutionary origins,from different ancestral genes.
D) They are dispersed on different chromosomes.
E) Some are expressed in all cells;some are expressed only in red blood cells.

Question 32

Which choice is not a characteristic of a plasmid used as a cloning vector?

A) confers a detectable property on a host cell
B) can be purified away from the host cell's genome
C) replicates independently
D) replicates itself and the inserted DNA
E) methylated to protect from digestion by host cell restriction enzymes

Question 33

The genetically determined molecular composition of haemoglobin changes several times during development including changing from embryonic,to fetal,to adult hemoglobin.

Question 34

A circular DNA of 1 kb length is cut with a restriction enzyme whose precise recognition sequence is not known.The digest yields four fragments of approximately equal size.What is the most likely conclusion from these data?

A) The enzyme is a 4-base cutter.
B) The enzyme is a 6-base cutter.
C) The enzyme is an 8-base cutter.
D) The enzyme leaves blunt ends.
E) This was a partial digest.

Question 35

When bacterial transformants containing a library are transferred to nitrocellulose filters and screened,one of the steps is treatment with an alkaline solution.What does this do?

A) attaches the library DNA to the nitrocellulose
B) promotes hybridization between the probe and complementary inserts
C) labels the DNA so it can be visualized
D) stimulates DNA replication,to increase the plasmid copy number
E) lyses the cells and denatures the released DNA

Question 36

A 16 kb linear DNA is cut with EcoRI and BamHI.The EcoRI digest yields fragments of 2,6,and 8 kb.The BamHI digest yields fragments of 5 and 11 kb.An EcoRI-BamHI double digest yields 2,3,5,and 6 kb fragments.The map of this DNA has

A) three EcoRI sites and two BamHI sites.
B) three BamHI sites and two EcoRI sites.
C) two EcoRI sites and two BamHI sites.
D) two EcoRI sites and one BamHI site.
E) one EcoRI site and two BamHI sites.

Question 37

Which technique is required to generate a restriction map?

A) electrophoresis
B) partial digestion with restriction enzymes
C) hybridization to a synthetic oligonucleotide probe
D) selection of recombinant bacteria by antibiotic resistance
E) transformation

Question 38

A 10 kb linear DNA is cut with EcoRI and HindIII.The EcoRI digest yields fragments of 2 and 8 kb.The HindIII digest yields fragments of 3 and 7 kb.What are the possible fragments (in kb)from an EcoRI-HindIII double digest?

A) 1,3,6 or 1,4,5
B) 1,4,5 or 1,2,7
C) 1,4,5,or 2,3,5
D) 1,2,7 or 1,3,6
E) 1,2,7 or 2,3,5

Question 39

What is the function of the amp^r gene in a vector?

A) It is a restriction enzyme recognition site.
B) It is a selectable marker.
C) It is the origin of replication.
D) It makes the enzyme ß-galactosidase if it is intact,indicating vectors without inserts.
E) It is required for packing into viral shells.

Question 40

In references to the "alpha-globin locus" or "beta-globin locus",the term "locus" means

A) a duplicated,ancestral gene.
B) a chromosome region with a cluster of related globin protein genes.
C) an alpha-,or a beta-globin protein with a single amino acid change.
D) the location,in this case red blood cells,where a mutant phenotype is manifested.
E) a geographical region where a genetic disease like sickle cell anemia is common.

Question 41

Antibiotic resistance genes are often used as selectable markers in vectors.

Question 42

The genomic equivalent of a library is determined by multiplying the number of clones on a plate by the size of the average insert.

Question 43

It is possible for two perfectly matched 50 bp DNA sequences from two different species to have arisen by chance.

Question 44

The formation of a recombinant DNA molecule occurs through the cutting and splicing together of a vector and a fragment of DNA from another origin.

Question 45

You wish to produce an abundance of protein for a gene you have just recently cloned from genomic DNA.How would you do this?

Question 46

A genomic library for an organism with a haploid genome of 5 × 10⁷ bp has fragments of approximately 20 kb.How many clones represent a single genomic equivalent?

Question 47

cDNA libraries are generated using a reverse transcriptase and represent the population of RNA transcripts initially contained in the cells used.

Question 48

Probability of a 6-base restriction enzyme site existing in a stretch of DNA is (1/6)⁴.

Question 49

Hybridization is the covalent binding of two complementary DNA strands.

Question 50

PCR makes a maximum of 1,000 perfect copies of the DNA being amplified in a day.

Question 51

List the components of a Sanger sequencing reaction.

Question 52

The restriction enzyme EcoRI cuts a linear 19 kb piece of DNA into fragments of 1,3,6,and 9 kb.How many EcoRI sites are there in the 19 kb piece of DNA?

Question 53

Which enzyme is used to generate DNA from RNA transcripts,for cDNA libraries?

Question 54

List two advantages of cDNA libraries over genomic libraries.

Question 55

List two reasons that partial digests are performed on genomic DNA when producing fragments for a library.

Question 56

PCR can be used to amplify DNA sequences of any size.

Question 57

Size of the recognition site and base composition of the genome affect fragment length produced by restriction enzymes.