SCYM Cell Cycle & DNA Content Analysis 2

Question 1

What is the primary reason RNase A is added to samples before propidium iodide staining for DNA content analysis?

Accepted Answer

To eliminate RNA that would otherwise contribute to PI fluorescence

Answer

PI intercalates into both double-stranded DNA and RNA; RNase A digests cellular RNA so that measured fluorescence reflects DNA content exclusively.

Question 2

Which fixation method is most commonly used to prepare cells for propidium iodide-based DNA content analysis?

Accepted Answer

Ice-cold 70% ethanol

Answer

Ice-cold 70% ethanol permeabilizes cells by precipitating membrane proteins, allowing PI uptake while preserving nuclear integrity and DNA content for accurate quantification.

Question 3

Aneuploid tumor cells are identified in DNA content analysis primarily by which characteristic?

Accepted Answer

DNA index significantly different from 1.0

Answer

Aneuploid cells carry an abnormal chromosome complement, placing their G0/G1 peak at a position different from the diploid reference, yielding a DNA index significantly different from 1.0.

Question 4

The proliferation index in cell cycle analysis is calculated using which cell cycle compartments?

Accepted Answer

S and G2/M fractions relative to all cells

Answer

The proliferation index = (S + G2/M) / (G0/G1 + S + G2/M), representing the proportion of cells that have committed to active cycling beyond the G1 gap phase.

Question 5

EdU (5-ethynyl-2'-deoxyuridine) is preferred over BrdU for S phase detection because EdU detection:

Accepted Answer

Uses click chemistry that does not require DNA denaturation

Answer

EdU contains a terminal alkyne that reacts with azide-fluorophore conjugates via copper-catalyzed click chemistry, eliminating the harsh acid or heat denaturation required to expose BrdU epitopes for antibody staining.

(SCYM) Specialist in Cytometry Practice Test

(SCYM) Specialist in Cytometry Practice Test

SCYM Cell Cycle & DNA Content Analysis 2