BIOD171 ESSENTIALS IN MICROBIOLOGY LAB MODULE 7 SECONDARY CHARACTERIZATION EXAM

BIO D171 LAB MICROBIOLOGY Module 7 Final Exam Review Q & A 2024 1. Which assay would be most appropriate for determining the concentration of bacterial endotoxins in a sample? - A. ELISA - B. Gel electrophoresis - C. Limulus Amebocyte Lysate (LAL) assay - D. Western blotting Answer: C. Limulus Amebocyte Lysate (LAL) assay Rationale: The LAL assay is specifically designed for detecting and quantifying bacterial endotoxins, which are components of the outer membrane of Gram -negative bacteria. 2. When performing a plaque assay to measure virus concentration, what does each plaque represent? - A. A single virus particle - B. A colony of bacteria - C. A cluster of infected cells - D. An antibody -antigen complex Answer: C. A cluster of infected cells Rationale: In a plaque assay, each plaque results from the infection of cells by a single virus particle, leading to a clear zone of lysed cells. 3. What is the primary purpose of a Bradford protein assay? - A. To identify specific proteins - B. To determine the nucleic acid content - C. To quantify total protein concentration - D. To assess enzyme activity Answer: C. To quantify total protein concentration Rationale: The Bradford protein assay is a colorimetric assay that measures the total protein concentration in a sample based on a color change. 4. Which secondary characterization assay is used to determine the size and purity of DNA fragments? - A. PCR amplification - B. Agarose gel electrophoresis - C. Flow cytometry - D. Mass spectrometry Answer: B. Agarose gel electrophoresis Rationale: Agarose gel electrophoresis separates DNA fragments by size and allows for the assessment of purity based on the clarity and distinctness of the bands. 5. In an enzyme -linked i mmunosorbent assay (ELISA), what is the role of the substrate? - A. To bind the antigen - B. To produce a detectable signal - C. To capture the antibody - D. To block nonspecific binding Answer: B. To produce a detectable signal Rationale : The substrate in an ELISA reacts with an enzyme linked to an antibody or antigen, producing a color change or other detectable signal indicating the presence of the target molecule. 6. What is the advantage of using a quantitative PCR (qPCR) over tradit ional PCR methods? - A. It requires less DNA template - B. It can run at lower temperatures - C. It provides quantitative data on DNA copy number - D. It eliminates the need for DNA primers Answer: C. It provides quantitative data on DNA copy number Rationale: qPCR allows for the quantification of DNA by measuring the fluorescence emitted during the reaction, which correlates with the amount of DNA amplified. 7. Which assay would be mo st suitable for detecting the presence of a specific protein in a complex mixture? - A. Bradford protein assay - B. Southern blot - C. Western blot - D. Spectrophotometry Answer: C. Western blot Rationale: The Western blot technique enabl es the detection and quantification of specific proteins using antibodies, even within a mixture of many different proteins.