Cell Cycle & DNA Content Analysis Flashcards
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Read the first 7 Cell Cycle & DNA Content Analysis flashcards as text
Which fluorescent dye is most commonly used for DNA content analysis in flow cytometry and requires RNase treatment for accurate results?
Answer: Propidium Iodide (PI)
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.
In a DNA content histogram, which cell cycle phase is represented by the 4N peak?
Answer: G2 and M phase
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.
What does a low coefficient of variation (CV) of the G0/G1 peak in a DNA histogram indicate?
Answer: Uniform DNA staining and good assay quality
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.
What is the DNA index (DI) of a normal diploid cell population used as a reference standard?
Answer: 1.0
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.
Which cell cycle phase is characterized by active DNA synthesis, with cells containing DNA content between 2N and 4N?
Answer: S phase
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.
Which DNA-binding dye can stain live cells without fixation because it is membrane-permeant?
Answer: Hoechst 33342
Hoechst 33342 is a cell-permeant bisbenzimide dye that binds AT-rich regions of dsDNA in the minor groove and can enter live cells, enabling DNA content analysis without fixation.
A sub-G1 peak in a DNA histogram is most commonly associated with which cellular process?
Answer: Apoptosis with DNA fragmentation
The sub-G1 peak represents apoptotic cells in which internucleosomal DNA cleavage by caspase-activated DNase has reduced total DNA content below the 2N level.