Quiz Ch. 15
Which of the following microbes can be readily used in treating a bacterial infection? A. A mutant strain of the same bacterium B. A phage with a lysogenic lifestyle C. A phage with a lytic lifestyle D. A R factor plasmid
C. A phage with a lytic lifestyle This phage will infect the cell and then kill the cell by breaking apart the DNA.
Which of the following viruses would mutate most readily? A. A virus with dsDNA genome B. A virus with ssDNA genome C. A virus with ssRNA genome D. A virus with naked helical capsid E. A virus with enveloped icosahedral capsid
C. A virus with ssRNA genome because RNA is a lot more unstable than DNA, causing a higher rate of mutation. viroid- An infectious agent with a small circular ssRNA genome lacking any gene for coat proteins. They do not require a helper virus for replication and never form particles.
An F- bacterium may receive part of the chromosomal DNA from a _______ bacterium? A. F+ B. F- C. Hfr D. F+ and hfr
C. Hfr A bacterium is called an hfr bacterium if the DNA genome of an F factor plasmid is inserted into the DNA genome of the bacterium. During conjugation, the plasmid DNA and part of the host chromosome of the hfr bacterium may transfer to the F- bacterium. Note that an F- cell can get only the F factor plasmid DNA but not any portion of the chromosomal DNA of a F+ cell.
A DNA polymerase committed a nucleotide substitution mutation in one of the two strands of the dsDNA molecule. If not corrected, which of the following would suffer the consequences? A. The mother cell. B. Both daughter cells. C. One of the two daughter cells. D. The mother cell and both daughter cells.
C. One of the two daughter cells. If a nucleotide mismatch is not repaired, DNA will be replicated and the mutation (base substitution) will become permanent in the genome of one of the daughter cells. (pg.219)
Influenza virus has eight genome fragments. The genome of the virus can evolve by mutations alone (called antigenic drift) or due to mixing of the genome fragments of different viruses (say human and chicken influenza viruses). This later method of evolution is called antigenic shift. The Asian Flu virus evolved through antigenic shift and it has chromosomes from human influenza virus and pig influenza virus. The Asian Flu virus evolved ________
because humans were simultaneously infected by the human influenza virus and the pig influenza virus
Is bacterial conjugation a mode sexual reproduction? A. No, because the cells do not fuse. B. Yes, because the process involves gene transfer. C. Yes, because only F+ and F- cells may conjugate. D. No, because the DNA exchange was one-way, not mutual.
A. No, b/c the cells do not fuse Note that bacterial conjugation is not a part of sexual reproduction. Conjugation in other microbes such as the protozoanParamecium and yeast does not involve an F factor. In Paramecium, two individual organisms come in a close embrace and exchange genetic materials (micronuclei) and then separate. Conjugation does not result in cellular fusion like gametes; the process does not involve cell division or reproduction. However, both partners receive new genetic materials in the process. (pg. 227)
Which of the following is a transversion type of mutation? A. Parental DNA 5CCGGAA3, daughter cell DNA 5CCGTAA3 B. Parental DNA 5CCGGAA3, daughter cell DNA 5CCGAAA3 C. Parental DNA 5CCGGAA3, daughter cell DNA 5CCGGAAA3 D. Parental DNA 5CCGGAA3, daughter cell DNA 5CCGAA3
A. Parental DNA 5CCGGAA3, daughter cell DNA 5CCGTAA3 In this strand, the guanine mutated into a thymine. In other words, the purine (G) mutated into the pyrimidine (T). The other strands mutate, but not from a purine to pyrimidine or vice versa. transversion mutation: A point mutation in which a pyrimidine is substitued for a purine, or vice versa. Purine: Adenine and Guanine Pyrimidine: cytosine, thymine, uracil
A plasmid was inserted in to an E. coli cell. The plasmid has a replication origin that can function in E. coli. What would most likely happen to the plasmid DNA? A. The plasmid would replicate and get distributed to the daughter cells as the cell divides. B. The plasmid would be recombined and integrated to the bacterial genome. C. The plasmid would be destroyed by the nucleases of the bacterium.
A. The plasmid would replicate and get distributed to the daughter cells as the cell divides. The plasmid has a replication origin. Plasmids replicate during cell growth and then are distribute to daughter cells vertically during binary fission. Some plasmids can be transferred horizontally (pg. 225) One of the strands of the plasmid DNA passes through the pilus to F- cell (Fig. 15.12). The single stranded plasmid DNA circularizes and then replicates to make a double-stranded F plasmid. Thus the F-recipient becomes F+ and the donor remains F+. If the donor is an F' cell, the F- cell would receive a piece of donor chromosome attached to the integrated F factor. However, the recipient cell may recombine the received chromosomal DNA to its own genomic DNA. Early bacterial geneticists varied the time of conjugation by shearing the conjugating Hfr and F- cells and developed a genetic map of E. coli.
Some DNA damaging agents and the mechanism of damage are listed below. Which of the statements is generally incorrect? A. UV light: Creates ions by breaking water molecules and the ions damage DNA. B. Methyl mercury: May donate the methyl group to a base of a nucleotide. C. Water: remove adenine or guanine bases away from a nucleotide. D. Water: removes the -NH2 group from A, G or C bases. E. Gamma radiation: Breaks the DNA backbone.
A. UV light: Creates ions by breaking water molecules and the ions damage DNA. UV: causes cross-linking (covalent bond formation). This mutation Radiation (Gamma/x-ray): creates ions by breaking water molecule. Breaks DNA backbone. Water: spontaneously loses -NH2 groups from A, G, or C. (Note that the loss of a NH2- group converts C to U and 5'methyl C to T. If not repaired before replication of the damaged DNA, the CG base pair of DNA would become an AT base pair in the next generation)
A Gram-negative bacterium is resistant to ampicillin because of having an F factor plasmid carrying an Amp- resistant gene. Can a Gram-positive bacterium living in the same environment obtain the intact plasmid? A. Yes, most likely through conjugation. B. Yes, most likely through transformation. C. Yes, most likely through generalized transduction. D. No, gene transfer between G-positive and G-negative cells does not take place.
A. Yes, most likely through conjugation (internet)
A lytic phage infected a bacterium. The offspring of the virus may transfer a gene of the infected bacterium to another bacterium by the process called _______ transduction. A. generalized B. specialized C. superimposed D. compromised
A. generalized
To survive (perpetuate) inside a cell, the plasmid must contain a ____________. A. replication origin B. circular dsDNA genome C. gene for the pilus protein D. gene for antibiotic resistance E. gene that codes for an antibiotic protein
A. replication origin pg.224 Plasmids are generally self-replicating, circular dsDNA. There are also some circular ssDNA plasmids and linear dsDNA plasmids in some bacteria.
Gene transfer among organisms that reproduce asexually is mostly ________ gene transfer. A. vertical B. horizontal C. lateral D. tangential E. circular
A. vertical Vertical gene transfer involves asexual reproduction (or cloning) or sexual reproduction (pg 217)
A human baby receives mitochondrial genes from her mother. This is an example of ____________ gene transfer. A. vertical B. horizontal C. lateral D. tangential E. circular
A. vertical Vertical gene transfer involves the transfer of genes from parent to offspring. (pg. 218) Horizontal or lateral gene transfer involves the transfer of genes from the environment or from cells that are unrelated (non-parental) cells.
Which of the following is a good definition of mutation?
Any change in the nucleotide sequences of the genome of a genome creature or a cell.
Which of the following bacteria would most likely be able to survive in a patient being treated with an antibiotic? A. A bacterial strain harboring an F factor. B. A bacterial strain harboring an R factor C. A bacterial strain harboring a dissimilation plasmid. D. A bacterial strain harboring a bacteriocinogenic plasmid.
B. A bacterial strain harboring an R factor Resistance Plasmid (R Factor): Plasmid containing one or more antibiotic resistance genes, also called R factors. Dissimilation Plasmid (D Factor): Plasmids containing unusual genes (that may metabolize toxic substances) Conjugative Plasmid (F for Fertility Factor): plasmid containing genes for sex pilus, can be transferred laterally, also called fertility (F) factor Bactericinogenic plasmid (B Factor): Plasmids containing genes that encode bacteriocins (bacteriocins- Bacterial proteins that inhibit growth of other related bacteria)
Which of the following plasmids will allow the host bacterium to become resistant to the antibiotic neomycin? A. F factor plasmid B. R factor plasmid C. D factor plasmid D. B factor plasmid
B. An R factor plasmid Resistance Plasmid (R Factor): Plasmid containing one or more antibiotic resistance genes, also called R factors. Dissimilation Plasmid (D Factor): Plasmids containing unusual genes (that may metabolize toxic substances) Conjugative Plasmid (F for Fertility Factor): plasmid containing genes for sex pilus, can be transferred laterally, also called fertility (F) factor Bactericinogenic plasmid (B Factor): Plasmids containing genes that encode bacteriocins (bacteriocins- Bacterial proteins that inhibit growth of other related bacteria)
Gamma radiation emitted by a radioisotope may damage DNA in any of the following manners except________. A. creating free radicals such as H₂O₂ B. chemically converting a G base to a C base C. breaking the sugar-phosphate backbone of DNA D. creating highly reactive ions through ionizing water
B. Chemically converting a G base to a C base (This is typical of water damage, not gamma radiation.) Gamma radiation creates free radicals like H₂O₂. It creates highly reactive ions the react with DNA by breaking its backbone.
Which of the following mutations is most likely the least harmful of the mutations? A. Transversion of a nucleotide in the RBS region of a mRNA gene B. Deletion of two nucleotides in the 3-prime UTR (untranslated region) C. Insertion of one nucleotide inside the ORF D. Transition of one nucleotide in the ORF
B. Deletion of two nucleotides in the 3-prime UTR (untranslated region) Deletion: If the mutation takes place in a spacer region (spaces between genes) it may not have any consequences to the organism. (pg 228) Such mutations are called silent mutations. If the mutation hits an important DNA signal, such as promoter, operator, terminator, splice signal, polyadenylation signal, ribosome binding site, etc., the signal element could remain unaffected, weakened or strengthened, depending on the nature of the nucleotide changes. Transversion: When a purine (A or G) is substituted by a pyrimidine (C or T) or vice versa. Could have various consequences depending on where the mutation took place in the genome. Base substitution is called transition when a purine (A and G) is substituted by a purine (G for A) or a pyrimidine (C and T) substituted by a pyrimidine (T for C). If the mutation hits within an ORF, the consequences could be diverse. Base substitution and insertion or deletion would have different consequences
Which of the following is a reasonable approach of keeping up with bacterial mutations through lateral gene transfer that often leads to bacterial antibiotic resistance? A. Stop using antibiotics altogether. B. Develop newer antibiotics on a regular basis. C. Develop antibacterial agents to remove all bacteria. D. Use bacteriophages to eliminate all pathogenic bacteria.
B. Develop newer antibiotics on a regular basis Option A is counterproductive because many bacteria are essential for healthy environments. Option A is also impractical because infected patients must be treated. Option C is impractical because bacteria will continue to evolve and new pathogenic bacteria will be generated. Option D is also impractical because there are many bacteriophages in the natural environments but pathogenic bacteria find ways to survive and flourish.
Which of the following statements is incorrect? A. Read-through (non-stop) mutation: The stop codon changed to a codon. B. Missense mutation: A codon changed to an anticodon. C. Nonsense mutation: A codon changed to a stop codon. D. Insertion mutation: Resulted into a frame shift. E. Deletion mutation: Resulted into a frame shift.
B. Missense mutation: A codon changed to an anticodon Missense: a nucleotide-pair substitution that results in a codon that codes for a different amino acid
Which of the following would contribute to replication errors the most? A. The cell contains more NTPs than dNTPs B. The DNA polymerase lacks the proofreading function C. There are some DNA intercalating agents inside the cell D. The temperature of the surroundings is 25 degrees Celsius, not the usual 15 degrees Celsius
B. The DNA polymerase lacks the proofreading function Cells have dedicated a significant amount of resources to prevent any damage or deterioration of the genome and to repair damaged DNA. Cellular DNA polymerases have a built- in system that corrects any mistakes in copying genomic DNA. Cells of metazoan organisms are so particular about integrity of the genome that if the cells sense that the DNA damage is beyond repair, the cell induces self extermination through a process called apoptosis. Interclating agent: A substance that inserts itself into the DNA structure of a cell and binds to the DNA. This causes DNA damage. In cancer treatment, DNA intercalating agents may kill cancer cells by damaging their DNA and stopping them from dividing.
Which of the following viruses would most likely cause a generalized transduction event? A. The virus infected the bacterium and became a provirus. B. The virus infected the bacterium, replicated inside the cell and killed the cell. C. The virus infected the bacterium, became a provirus and later left the bacterial genome
B. The virus infected the bacterium, replicated inside the cell and killed the cell. pg. 223-224 - Gene transfer by a lytic virus is called generalized transduction; In a lytic infection (shown by black arrows), the phage quickly express its genes and breaks host DNA into small pieces. During phage assembly, some fragments of host DNA may be accidentally packed in phage particles. The phage may infect another bacterium and deliver a fragment of DNA from the previous host bacterium to the new host bacterium. - gene transfer by a lysogenic virus is called specialized transduction. The high abundance of bacteriophages in the natural environment makes both generalized and specialized transduction important methods of gene transfer among bacteria. - In the lysogenic cycle (specialized transduction), the virus expresses only a limited number of viral genes. Some of the viral proteins and some of the host cell protein recombine the viral genome to the host genome. The integrated virus genome is called a provirus and the host cell is called a lysogen. - The viral genome remains in the lysogen and transmits to the offspring of the lysogen. If the lysogen fails to replicate DNA, the virus genome manages to cut itself out of the host genome and completes a lytic cycle (Fig. 15.10). - Phages generated through both lytic and lysogenic cycles may transfer DNA of one host cell to the next host cell.
Which of the following is the best practice on antibiotics use? A. Stop using antibiotics altogether. B. Use antibiotics in treating infections, not in animal feeds. C. Use antibiotics in animal feeds but in a very high dose that kills 100% of the pathogenic bacteria. D. Use a mixture of multiple antibiotics in animal feeds at a high dose that kills 100% of the pathogenic bacteria.
B. Use antibiotics in treating infections, not in animal feeds.
The eukaryotic pathogens such as fungal and protozoan parasites evolve relatively slowly and become drug- resistant less frequently, most likely because the eukaryotic parasites _________. A. have an inferior proofreading system to correct DNA replication errors compared to that of bacteria and viruses. B. have a better proofreading system to correct DNA replication errors compared to that of bacteria and viruses. C. are not exposed to harsh environmental conditions and mutagens as the bacterial and viral pathogens D. they infrequently come in contact of humans
B. have a better proofreading system to correct DNA replication errors compared to that of bacteria and viruses.
Mutations may cause each of the following problems except__________. A. prevent translation or change the function of the protein B. prevent evolution through natural selection C. eliminate the organism from the population D. prevent DNA replication or transcription E. alter the controls of gene expression
B. prevent evolution through natural selection - The majority of the mutations are deleterious because mutant genes are not the best fit to the current environment. Mutation in the somatic cells (non-reproductive cells) of a metazoan organism may ruin the organism. - Cancers and many metabolic diseases are due to such mutations. Mutations in the germline may destroy a species and/ or help evolve new species. Mutations are mostly random, continuous and unavoidable. Mutations of a species may affect other species and the environment as a whole. - mutation is the driving force of the biodiversity (creation of many species) and the continuous existence of life on earth.
A Corynebacterium has a bacteriophage inserted in its genome. Which of the following entities is the lysogen? A. The virus B. The bacterium C. The virus and the bacterium D. The child infected by the bacterium
B. the bacterium the lysogen is the host cell
A linear piece of DNA lacking a replication origin was inserted to an E. coli cell. The nucleotide sequence of the inserted piece is somewhat similar to a gene of the E. coli cell. What would NOT happen to the inserted DNA? A. The inserted DNA would be destroyed by the nucleases of the cell. B. The inserted DNA would replicate and distributed to the daughter cells. C. Part of one of the two strands of the DNA will be recombined into the E. coli genome.
C. Part of one of the two strands of the DNA will be recombined into the E. coli genome. Plasmids need the replication origin in order to survive in the cell and replicate. (pg. 227) The DNA fragment lacked an origin but it is very similar in DNA sequence to one of the genes of the recipient cell. Option A would have happened if the DNA fragment were totally foreign to the host cell. Option B is also possible but less likely.
The bacterium Pasteurella multocida infected seagulls living in the Easter Island (of the south Pacific Ocean), sea gulls living in the Utah Lake and chickens living in the Twyla Industrial Chicken Farm. Which of the bacteria may become readily antibiotic resistant? A. The bacterium that infected seagulls of Easter Island B. The bacterium that infected seagulls of the Utah Lake C. The bacterium that infected chickens of the Twyla Industrial Chicken Farm
C. The bacterium that infected chickens of the Twyla Industrial Chicken Farm Smaller pool = less variation = higher antibiotic resistance Bacterial strains become antibiotic resistant usually if the bacteria are exposed to antibiotics. Chicken raised in industrial farms feed on antibiotic-laced food. Seagulls living in Utah Lake may also get exposed to antibiotics by eating chicken feed from the industrial feed lots.
Which of the following beef burgers carries the highest potential infection risks? Note: All the burgers were processed and cooked medium rare under identical conditions. A. The beef was from a grass-fed cow B. The cow was treated with antibiotics six months ago C. The beef was from several different cows from different industrial feeding lots D. The cow was genetically engineered and the cattle were raised in a controlled environment
C. The beef was from several different cows from different industrial feeding lots Since different beef samples could have different bacterial strains carrying the F factor plasmids, the bacteria may conjugate with each other, transfer the disease-causing genes to generate highly pathogenic strains of bacteria. Option B also carries the potential of generating drug-resistant bacteria.
A plant was infected by a bacterium. The plant survived the infection and the bacterium was eliminated from the system of the plant. However, genetic analysis indicated the presence of the some of the bacterial genes in the nuclei of some of the seeds of the plant. This is an example of ____________. A. vertical B. horizontal C. lateral or horizontal D. tangential or bilateral
C. lateral or horizontal
You want to insert a human gene inside a bacterium. Which of the following processes will be the least helpful one in achieving your goal? A. Momentarily pulse the cells with a high electric voltage. B. Pack the DNA in a lipid vesicle and mix it with the bacterial cell. C. Momentarily treat the cell with higher temperature (42 degrees C for 30 sec.). D. Add the DNA to a solution containing anions (such as SDS) and mix it with the bacterial cell. E. Add the DNA to a solution containing some cations (such as Ca++) and mix it with the bacterial cell
D. Add the DNA to a solution containing anions (such as SDS) and mix it with the bacterial cell. This is a question about transfection. metal ions (Ca++) are helpful to the process of transfection and may neutralize DNA or the cell surface and allow DNA to fall on the cell surface. Some bacterial cells develop a physiological state called competence when the cells can pick up nucleic acid from the environment. If foreign DNA is mixed with a positively charged molecule such as CaCl (i.e. Ca++ ions), some of the cells will uptake foreign DNA. The process of causing a cell to uptake foreign DNA is transfection
Which of the following is a good definition of mutation? A. Any change in the activity of a protein of a cell. B. Any change in the phenotype of an organism or a cell. C. Any change in the rate of expression of a gene of a cell. D. Any change in the nucleotide sequences of the genome of a cell.
D. Any change in the nucleotide sequences of the genome of a cell. Mutations are inherited through vertical gene transfer.
Which of the following organisms (all belong to the bacterial species Corynebacterium diphtheriae) has most likely become a lysogen? A. The size of the bacterial genome was 4.5 mbp, now the genome is 4.7 mbp. B. The bacterium caused diphtheria in a child. C. The bacterium has a provirus. D. Any of these bacteria
D. Any of these bacteria pg. 224 lysogenic = provirus Lysogenic phages may convert an otherwise nonpathogenic bacterium to a pathogenic one scarlet fever (caused by some strains of Streptococcus pyogenes), botulism (caused by some strains of Clostridium botulinum), and staphylococcal toxins responsible for food poisoning (caused by certain strains of Staphylococcus aureus) are results of lysogenic conversion. Diphtheria is caused by a bacterium, Corynebacterium diphtheriae. The actual disease is caused when the bacte- ria release a toxin, or poison, into a person's body. Diphtheria bacteria live in the mouth, throat, and nose of an infected person and can be passed to others by coughing or sneezing.
Which of the following mobile genetic elements can be moved by a transposase enzyme? A. LINE and SINE. B. Any of the elements. C. Retroviruses and LTR elements. D. DNA transposons and insertion sequences (IS).
D. DNA transposons and insertion sequences (IS) (per the answers at the back of the book) DNA transposons are moved from one location of the genome to another by enzymes called transposase coded by the transposon. SINE, LINE, retroviruses and retrovirus remnants are moved through an RNA intermediate. (pg 230)
A person is infected simultaneously by human and avian influenza viruses. Which of the following viruses generated in the cells of the person has undergone an antigenic shift. A. The virus has all the human influenza virus genome fragments, some fragments are mutated B. The virus has only the avian influenza virus genome fragments, some fragments are mutated C. The virus has some human influenza virus genome fragments and some avian influenza virus genome fragments, some of the genome fragments are mutated. D. The virus has some human influenza virus genome fragments and some avian influenza virus genome fragments, none of the genome fragments are mutated.
D. The virus has some human influenza virus genome fragments and some avian influenza virus genome fragments, none of the genome fragments are mutated. The new virus has genome fragments from two different species of the virus. Options A and B are examples of antigenic drift. Option is C is incorrect because it is an event of coupled antigenic drift and shift.
A porcine influenza virus has infected a pig. The virus has mutated one of its eight genome fragments. This mutation may lead to ______. A. antigenic drift B. antigenic shift C. demise of the virus D. antigenic drift or shift E. antigenic drift or demise of the virus
E. antigenic drift or demise of the virus RNA viruses with segmented genomes, such as the influenza virus present an unusual mode of variation. The influenza virus genome is distributed in eight antisense RNA fragments. The fragments may accumulate mutations over time and generate new strains of viruses. Such gradual variation among influenza viruses is called genetic drift. genetic Drift: gradual mutation over time creating new strains of viruses. genetic Shift: mixed and matched assembly is genetic shift and drastically alters the viral genome. Several influenza pandemics that killed millions of people in the past are believed to be caused by virus strains originated through genetic shift. Infection of a cell with two different virus species is called a superinfection. Some of the progeny viruses assembled in the host cell may contain some of the genome fragments from both strains of viruses. The pig is infected by only one type of the influenza virus. The mutation may destroy the virus or change the structure and functions of some of the antigens the virus. There is no chance of mixing the genomes of two or more types of viruses to create antigenic shift.