Question 1

Which of the following best describes the main difference between direct and indirect immunofluorescence techniques?

Accepted Answer

Direct immunofluorescence uses a fluorophore-conjugated primary antibody, while indirect immunofluorescence uses a non-fluorescent primary antibody and a fluorophore-conjugated secondary antibody.

Question 2

A researcher uses flow cytometry with propidium iodide staining to analyze a population of cells. What property of the cells is being measured, and what can this reveal about the cell cycle?

Accepted Answer

The DNA content of each cell, which can be used to determine the proportion of cells in G₁, S, and G₂/M phases.

Question 3

Which of the following statements about the Stokes shift in fluorescence is correct?

Accepted Answer

The Stokes shift is the difference in wavelength between the excitation and emission maxima of a fluorophore.

Question 4

A tumor biopsy is stained for Ki-67. What does a high Ki-67 index indicate about the tumor?

Accepted Answer

The tumor has a high proportion of actively dividing cells and is likely to be rapidly growing.

Question 5

Which experimental technique would be most appropriate for quantifying the percentage of cells in mitosis in a tissue section?

Accepted Answer

Microscopy-based analysis using mitotic index calculation.

Question 6

Why is BrdU (5'-bromo-2'-deoxyuridine) used in cell cycle studies, and during which phase is it incorporated into DNA?

Accepted Answer

BrdU is a thymidine analogue incorporated during S phase, allowing identification of replicating cells.

Question 7

A scientist uses GFP-tagged histone proteins to visualize chromosomes in living cells. What is the main advantage of this approach compared to traditional staining methods?

Accepted Answer

It allows real-time observation of chromosome dynamics in living cells.

Question 8

Which of the following best explains why fluorescence microscopy is preferred over brightfield microscopy for studying specific proteins in cells?

Accepted Answer

Fluorescence microscopy allows for the specific labeling and visualization of target proteins using fluorophore-conjugated antibodies.

Question 9

A flow cytometry histogram shows two peaks: one at 2N and one at 4N DNA content. What do these peaks represent?

Accepted Answer

Cells in G₁ phase (2N) and cells in G₂/M phase (4N).

Question 10

Which of the following is a limitation of using the mitotic index as a measure of cell proliferation in tumor samples?

Accepted Answer

Mitotic activity may vary within different regions of a tumor, leading to sampling bias.

Question 11

Which of the following best describes the process of fluorescence in a fluorophore?

Accepted Answer

A fluorophore absorbs light at a specific excitation wavelength, its electrons become excited, and then it emits light at a longer wavelength as the electrons return to the ground state.

Question 12

A cell population is treated with a drug that blocks the transition from G₂ to M phase. Which experimental method would best confirm the accumulation of cells at this checkpoint?

Accepted Answer

Flow cytometry analysis of DNA content, showing increased cells with 4N DNA.

Question 13

Which of the following is a key advantage of using genetically encoded fluorescent proteins (such as GFP) for studying cell cycle progression?

Accepted Answer

They allow for non-invasive, real-time tracking of protein localization and cell cycle events in living cells.

Question 14

A researcher wants to distinguish between cells in G₀/G₁, S, and G₂/M phases in a large population. Which combination of techniques would provide the most quantitative and high-throughput data?

Accepted Answer

Flow cytometry with DNA-binding fluorescent dyes.

Question 15

Which of the following best explains why a fluorophore emits light at a longer wavelength than the excitation light?

Accepted Answer

Some energy is lost as heat when the electron returns to the ground state, resulting in emission of a lower energy (longer wavelength) photon.

Question 16

Which of the following scenarios would most likely result in aneuploidy detectable by flow cytometry?

Accepted Answer

A failure in chromosome segregation during mitosis, leading to cells with abnormal DNA content.

Question 17

A scientist uses the FUCCI system to visualize cell cycle progression in live cells. What is the principle behind this system?

Accepted Answer

It uses fluorescent proteins fused to cell cycle regulators that are degraded at specific phases, allowing visualization of cell cycle transitions.

Question 18

Which of the following is a potential source of error when using immunohistochemistry (IHC) to assess cell proliferation in tumor samples?

Accepted Answer

Inter-observer variation in scoring stained cells.

Experimental Techniques to Analyze Cell Division and DNA Content in Eukaryotic Cells

Study Guide - Practice Questions

Study Guide - Flashcards