Tuberculosis (TB) is caused by the acid-fast bacterium Mycobacterium tuberculosis. Although most TB cases affect the lungs (pulmonary TB), some infections occur in other body sites (extrapulmonary TB). Among these cases, lymph node tuberculosis (LNTB) is the most common. Diagnosis of LNTB by conventional methods (staining, biochemical tests) has limitations—for example, formaldehyde preservation of tissue biopsies interferes with the acid-fast stain, leading to underdiagnosis or misdiagnosis. Now fluorescent in situ hybridization (FISH) is being used to diagnose extrapulmonary TB.

-When a tissue sample such as lymph node tissue is to be analyzed by FISH, it must first be treated with chemicals. Which of the following is NOT a reason that this step is needed?
A) To maintain cell shape.
B) To inactivate enzymes that might otherwise degrade the nucleic acid of the cells.
C) To make the cells more permeable so that the labeled probe can easily enter.
D) To inactivate enzymes that might otherwise degrade the nucleic acid of the cells AND to maintain cell shape.
E) To break down the cellulose walls of the tissue so that the probes can enter those cells.

Question

Tuberculosis (TB) is caused by the acid-fast bacterium Mycobacterium tuberculosis. Although most TB cases affect the lungs (pulmonary TB) , some infections occur in other body sites (extrapulmonary TB) . Among these cases, lymph node tuberculosis (LNTB) is the most common. Diagnosis of LNTB by conventional methods (staining, biochemical tests) has limitations—for example, formaldehyde preservation of tissue biopsies interferes with the acid-fast stain, leading to underdiagnosis or misdiagnosis. Now fluorescent in situ hybridization (FISH) is being used to diagnose extrapulmonary TB.

-When a tissue sample such as lymph node tissue is to be analyzed by FISH, it must first be treated with chemicals. Which of the following is NOT a reason that this step is needed?

-When a tissue sample such as lymph node tissue is to be analyzed by FISH, it must first be treated with chemicals. Which of the following is NOT a reason that this step is needed?
A) To maintain cell shape.
B) To inactivate enzymes that might otherwise degrade the nucleic acid of the cells.
C) To make the cells more permeable so that the labeled probe can easily enter.
D) To inactivate enzymes that might otherwise degrade the nucleic acid of the cells AND to maintain cell shape.
E) To break down the cellulose walls of the tissue so that the probes can enter those cells.

Quizplus · Accepted Answer

Chemical treatment is not needed to maintain cell shape or inactivate enzymes that might degrade nucleic acids. Rather, it is needed to break down cellulose walls of the tissue so that the probes can enter the cells.

Tuberculosis (TB) Is Caused by the Acid-Fast Bacterium Mycobacterium Tuberculosis