SCYM Cell Cycle & DNA Content Analysis

Question 1

Which fluorescent dye is most commonly used for DNA content analysis in flow cytometry and requires RNase treatment for accurate results?

Accepted Answer

Propidium Iodide (PI)

Answer

Propidium iodide intercalates into double-stranded nucleic acids including RNA, so RNase A treatment is required to eliminate RNA-derived signal and ensure fluorescence reflects only DNA content.

Question 2

In a DNA content histogram, which cell cycle phase is represented by the 4N peak?

Accepted Answer

G2 and M phase

Answer

Cells in G2 and M phases have completed DNA replication and contain exactly twice the diploid (2N) DNA content, producing the 4N peak in a DNA histogram.

Question 3

What does a low coefficient of variation (CV) of the G0/G1 peak in a DNA histogram indicate?

Accepted Answer

Uniform DNA staining and good assay quality

Answer

A low CV of the G0/G1 peak reflects homogeneous DNA staining, optimal sample preparation, and high instrument precision, indicating a high-quality DNA content assay.

Question 4

What is the DNA index (DI) of a normal diploid cell population used as a reference standard?

Accepted Answer

1.0

Answer

The DNA index is the ratio of the G0/G1 peak position of the test cells to a diploid reference standard; normal diploid cells have a DI of exactly 1.0.

Question 5

Which cell cycle phase is characterized by active DNA synthesis, with cells containing DNA content between 2N and 4N?

Accepted Answer

S phase

Answer

S phase (synthesis phase) is when the cell replicates its entire genome, resulting in a continuous distribution of DNA content between 2N and 4N that forms the S phase fraction in a histogram.

(SCYM) Specialist in Cytometry Practice Test

(SCYM) Specialist in Cytometry Practice Test

SCYM Cell Cycle & DNA Content Analysis