Block 9 Micro Dr Schleg Questions Prt 1
- 1.
Which of the following describes the majority of human pathogens?
- A.
Anaerobic mesophiles
- B.
Neutrophilic mesophiles
- C.
Neutrophilic aerophiles
- D.
Osmotolerant anaerobes
- E.
Osmotolerant aerophiles
Correct Answer
B. Neutrophilic mesophilesExplanation
Neutrophilic mesophiles describe the majority of human pathogens. Neutrophilic refers to organisms that prefer a neutral pH, which is similar to the pH of the human body. Mesophiles are organisms that grow best at moderate temperatures, typically between 20-45 degrees Celsius, which is the range of temperatures found in the human body. Therefore, neutrophilic mesophiles are well-suited to survive and thrive in the human body, making them the most common type of pathogens that cause diseases in humans.Rate this question:
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- 2.
A sample of pus aspirated from a patient’s abdominal abscess was sent to the diagnostic laboratory, where isolation was attempted under aerobic and anaerobic conditions. If the organism were a facultative anaerobe, which pattern of growth would you expect?
- A.
Growth on aerobic plate only
- B.
Growth on both plates
- C.
Growth on the anaerobic plate only
- D.
Growth on neither plate
Correct Answer
B. Growth on both platesExplanation
If the organism is a facultative anaerobe, it means that it can survive and grow in both aerobic and anaerobic environments. Therefore, you would expect to see growth on both the aerobic plate and the anaerobic plate.Rate this question:
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- 3.
If the organism above were a microaerophile, which would you expect?
- A.
Growth on aerobic plate only
- B.
Growth on both plates
- C.
Growth on the anaerobic plate only
- D.
Growth on neither plate
- E.
Growth on the anaerobic plate, poor growth on the aerobic plate
Correct Answer
E. Growth on the anaerobic plate, poor growth on the aerobic plateExplanation
If the organism is a microaerophile, it means that it requires low levels of oxygen to grow. Therefore, it would be expected to show growth on the anaerobic plate, which lacks oxygen. However, it would exhibit poor growth on the aerobic plate, which contains higher levels of oxygen that are not suitable for its growth requirements.Rate this question:
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- 4.
Which of the following is found at the 3' position of a nucleotide and missing in Acyclovir?
- A.
A phosphate group
- B.
A hydrogen
- C.
A hydroxyl group
- D.
Histones
Correct Answer
C. A hydroxyl groupExplanation
Acyclovir is an antiviral medication that is commonly used to treat herpes infections. Nucleotides are the building blocks of DNA, and each nucleotide consists of a sugar molecule, a phosphate group, and a nitrogenous base. The 3' position of a nucleotide refers to the carbon atom on the sugar molecule that is attached to the phosphate group. In Acyclovir, this position lacks a hydroxyl group (-OH) which is usually present in a regular nucleotide. The absence of the hydroxyl group at the 3' position is an important modification that allows Acyclovir to inhibit viral DNA replication.Rate this question:
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- 5.
Which of the following nutrients is sequestered by the mammalian system as a protective mechanism and is often the rate-limiting nutrient for bacterial growth?
- A.
Selenium
- B.
Glucose
- C.
Fatty acids
- D.
Molybdenum
- E.
Iron
Correct Answer
E. IronExplanation
Iron is sequestered by the mammalian system as a protective mechanism and is often the rate-limiting nutrient for bacterial growth. This means that the body tightly regulates iron levels to prevent bacteria from accessing it and using it for their own growth. Iron is essential for many biological processes, including bacterial growth, so by sequestering iron, the body can limit bacterial growth and prevent infections.Rate this question:
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- 6.
A bacterium has just activated the Fur global regulator. What is the organism producing and why?
- A.
Slime exopolysaccharide, to form a biofilm
- B.
Siderophores, to acquire iron
- C.
Heme-binding proteins, to adhere to red blood cells
- D.
Flagella, to move away from toxins
- E.
Fermentative enzymes, to utilize a new sugar source
Correct Answer
B. Siderophores, to acquire ironExplanation
When the Fur global regulator is activated in a bacterium, it produces siderophores. Siderophores are molecules that help the bacterium acquire iron. Iron is an essential nutrient for bacteria, but it is often limited in the environment. Siderophores are produced to scavenge and bind to iron, allowing the bacterium to acquire this important nutrient for its survival and growth.Rate this question:
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- 7.
All of the following are true statements concerning plasmids EXCEPT:
- A.
They can replicate autonomously
- B.
They can carry genes that confer resistance against antibiotics
- C.
They can be found in bacteria, fungi, and protozoa
- D.
They are small circular molecules of DNA
- E.
They carry genes that are required for growth and repair
Correct Answer
E. They carry genes that are required for growth and repairExplanation
Plasmids are small circular molecules of DNA that can replicate autonomously. They can carry genes that confer resistance against antibiotics. They can be found in bacteria, fungi, and protozoa. However, plasmids do not carry genes that are required for growth and repair. These genes are typically found in the chromosomal DNA of the organism. Therefore, the statement "They carry genes that are required for growth and repair" is not true for plasmids.Rate this question:
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- 8.
DNA ligase
- A.
Breaks hydrogen bonds between complementary nucleotides.
- B.
Synthesizes short DNA molecules important for the function of DNA polymerase
- C.
Seals gaps between DNA fragments
- D.
Proofreads DNA molecules
- E.
Assists in recognition of promoters during transcription.
Correct Answer
C. Seals gaps between DNA fragmentsExplanation
DNA ligase is an enzyme that plays a crucial role in DNA replication and repair. It is responsible for sealing the gaps between DNA fragments, which occur during processes such as DNA replication or DNA repair. When DNA is damaged or fragmented, DNA ligase helps in joining the broken ends by forming phosphodiester bonds between adjacent nucleotides. This ensures that the DNA molecule is intact and functional. Therefore, the correct answer is that DNA ligase seals gaps between DNA fragments.Rate this question:
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- 9.
All of the following statements concerning transcription in bacteria are true EXCEPT:
- A.
It occurs in the nucleoid region
- B.
Sigma factors are parts of RNA polymerase that recognize promoter regions.
- C.
There is only a unique sigma factor, which is termed Rho protein
- D.
Termination is either self-induced or due to the presence of Rho protein
- E.
A variety of sigma factors affect transcription
Correct Answer
C. There is only a unique sigma factor, which is termed Rho proteinExplanation
The statement that there is only a unique sigma factor, which is termed Rho protein, is incorrect. Rho protein is actually a termination factor, not a sigma factor. Sigma factors are responsible for recognizing promoter regions and initiating transcription in bacteria. There are multiple sigma factors that can bind to RNA polymerase and direct it to different promoter sequences, allowing for the regulation of gene expression.Rate this question:
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- 10.
Which of the following is involved in translation?
- A.
RRNA
- B.
TRNA
- C.
MRNA
- D.
Both A and C are correct.
- E.
A, B, and C are correct
Correct Answer
E. A, B, and C are correctExplanation
Translation is the process in which the genetic information carried by mRNA is decoded to produce proteins. During translation, ribosomal RNA (rRNA) and transfer RNA (tRNA) play crucial roles. rRNA is a component of ribosomes, which are the cellular structures responsible for protein synthesis. tRNA molecules carry amino acids to the ribosomes, where they are assembled into a polypeptide chain according to the instructions encoded in the mRNA. Therefore, all three options, A (rRNA), B (tRNA), and C (mRNA), are involved in translation.Rate this question:
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- 11.
RNA polymerase and DNA polymerase differ from each other in all of the following ways EXCEPT:
- A.
Efficiency of proofreading
- B.
Type of nucleotides used
- C.
Direction of polymerization.
- D.
Termination.
- E.
Dependence on sigma factors
Correct Answer
C. Direction of polymerization.Explanation
RNA polymerase and DNA polymerase differ from each other in the efficiency of proofreading, the type of nucleotides used, termination, and dependence on sigma factors. However, they do not differ in the direction of polymerization. Both RNA polymerase and DNA polymerase synthesize nucleic acids in the 5' to 3' direction.Rate this question:
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- 12.
An organism uses a fermentative pathway to acquire energy, but is able to detoxify small amounts of oxygen due to the expression of a peroxidase enzyme. It would be classified as:
- A.
A strict aerobe
- B.
A microaerophile
- C.
Facultative anaerobe
- D.
An aerotolerant anaerobe
- E.
A strict anaerobe
Correct Answer
D. An aerotolerant anaerobeExplanation
An aerotolerant anaerobe is an organism that can survive in the presence of oxygen but does not use it for energy production. In this case, the organism uses a fermentative pathway to acquire energy, indicating that it does not rely on oxygen for metabolism. However, it is able to detoxify small amounts of oxygen due to the expression of a peroxidase enzyme. This ability to tolerate oxygen without utilizing it for energy classifies the organism as an aerotolerant anaerobe.Rate this question:
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- 13.
In addition to coding for the amino acid methionine, what function does the codon AUG serve?
- A.
Termination signal
- B.
Start signal
- C.
Causes "wobble"
- D.
Marker for introns
- E.
Recognition site for RNA polymerase
Correct Answer
B. Start signalExplanation
The codon AUG serves as a start signal in addition to coding for the amino acid methionine. This means that it is the signal for the beginning of protein synthesis in mRNA. When the ribosome encounters the AUG codon, it starts translating the mRNA and synthesizing the protein from that point onwards.Rate this question:
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- 14.
The binding of sigma factors improves the specificity of a multiprotein complex that carries out which process?
- A.
Conjugation
- B.
Type III secretion
- C.
DNA replication
- D.
Transcription
- E.
Translation
Correct Answer
D. TranscriptionExplanation
The binding of sigma factors to a multiprotein complex improves the specificity of the complex in carrying out the process of transcription. Sigma factors are proteins that help RNA polymerase recognize and bind to specific DNA sequences, known as promoters, to initiate transcription. By binding to the multiprotein complex, sigma factors enhance the ability of RNA polymerase to accurately initiate transcription at the appropriate genes, thereby increasing the specificity of the transcription process.Rate this question:
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- 15.
During translation, an mRNA codon will pass through which of the following sequences of tRNA binding sites on the ribosome?
- A.
A site, E site, P site
- B.
E site, P site, A site
- C.
P site, E site, A site
- D.
A site, P site, E site
- E.
P site, A site, E site
Correct Answer
D. A site, P site, E siteExplanation
During translation, an mRNA codon will pass through the A site, P site, and E site on the ribosome. The A site (aminoacyl site) is where the incoming aminoacyl-tRNA binds to the ribosome. The P site (peptidyl site) is where the growing polypeptide chain is held by the tRNA. The E site (exit site) is where the tRNA exits the ribosome after its amino acid has been added to the polypeptide chain. This sequence of tRNA binding sites allows for the proper elongation of the polypeptide chain during translation.Rate this question:
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- 16.
Semiconservative DNA replication means that
- A.
Each daughter DNA molecule is composed of one original strand and one new strand.
- B.
Nucleotides are constantly being recycled as cells make DNA.
- C.
The cell can proofread its newly synthesized DNA part of the time
- D.
The sequence of a DNA molecule is preserved as it is being replicated.
- E.
Each strand of a double-stranded DNA molecule is replicated differently
Correct Answer
A. Each daughter DNA molecule is composed of one original strand and one new strand.Explanation
Semiconservative DNA replication means that each daughter DNA molecule is composed of one original strand and one new strand. During replication, the DNA double helix unwinds and each original strand serves as a template for the synthesis of a new complementary strand. This process ensures that the genetic information is preserved and passed on to the next generation of cells.Rate this question:
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- 17.
Which of the following protein secretion pathways is most commonly used by Gram-positive bacteria?
- A.
Type II secretion
- B.
Type I secretion
- C.
General secretion
- D.
Type IV secretion
- E.
Main terminal branch
Correct Answer
C. General secretionExplanation
Gram-positive bacteria commonly use the general secretion pathway for protein secretion. This pathway, also known as the Sec pathway, is found in all bacteria and is responsible for the translocation of proteins across the cytoplasmic membrane. It involves the use of a signal sequence on the protein that directs it to the Sec machinery, which then facilitates its transport across the membrane. This pathway is essential for the secretion of a wide range of proteins, including enzymes, toxins, and cell surface proteins, and is therefore commonly used by Gram-positive bacteria for their protein secretion needs.Rate this question:
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- 18.
All of the following are characteristics of Okazaki fragments EXCEPT:
- A.
They are checked for accuracy by DNA polymerase III.
- B.
They make up the lagging strand of replicated DNA.
- C.
They begin with an RNA primer
- D.
They are joined together by DNA ligase
- E.
They do not exist in eukaryotic cells
Correct Answer
E. They do not exist in eukaryotic cellsExplanation
Okazaki fragments are short segments of DNA that are synthesized on the lagging strand during DNA replication. They are formed because DNA polymerase can only synthesize DNA in the 5' to 3' direction, while the lagging strand is oriented in the opposite direction. Therefore, the lagging strand is synthesized in short fragments that are later joined together by DNA ligase. Okazaki fragments begin with an RNA primer, which is later replaced with DNA. While Okazaki fragments are present in prokaryotic cells, they do not exist in eukaryotic cells, as eukaryotic DNA replication occurs differently.Rate this question:
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- 19.
If the codon AAA is changed to UAA, it no longer codes for an amino acid; instead, it becomes a stop codon that signals translation termination in a protein. This is an example of a
- A.
Silent mutation
- B.
Nonsense mutation
- C.
Frameshift mutation
- D.
Gross mutation
- E.
Missense mutation
Correct Answer
B. Nonsense mutationExplanation
The change of the codon AAA to UAA in this scenario results in a nonsense mutation. This is because the codon UAA is a stop codon, which signals the termination of translation in a protein. In contrast, the original codon AAA codes for an amino acid. Therefore, this mutation changes the meaning of the codon from coding for an amino acid to signaling the end of translation.Rate this question:
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- 20.
Gene transfer
- A.
Involves the transfer of DNA from a donor cell to a recipient cell.
- B.
Can involve several mechanisms
- C.
Occurs only between cells of the same species.
- D.
Both A and B are correct
- E.
A, B, and C are correct.
Correct Answer
D. Both A and B are correctExplanation
Gene transfer involves the transfer of DNA from a donor cell to a recipient cell. This process can occur through several mechanisms, such as conjugation, transformation, and transduction. These mechanisms allow for the transfer of genetic material between cells, regardless of whether they are of the same species or not. Therefore, both options A and B are correct.Rate this question:
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