SCYM Instrument Operation 3

Question 1

A technologist observes that FSC and SSC populations appear dimmer than usual and events are fewer than expected. The most likely instrument issue is:

Accepted Answer

Laser misalignment or reduced laser power

Answer

Reduced FSC/SSC signal intensity combined with lower event counts strongly suggests laser misalignment or power loss at the interrogation point.

Question 2

In electrostatic cell sorting, cells are deflected into collection tubes by:

Accepted Answer

Charged droplets passing through an electrostatic deflection field

Answer

In electrostatic sorting, droplets containing target cells are given an electrical charge and deflected by high-voltage plates into collection vessels.

Question 3

Which type of flow cytometer detector is most commonly used to measure fluorescence signals?

Accepted Answer

Photomultiplier tube (PMT)

Answer

PMTs are the standard fluorescence detectors in flow cytometry because of their high sensitivity and ability to amplify low-level photon signals.

Question 4

What is the recommended maximum number of cells per milliliter in the sample tube to avoid coincident events in most standard flow cytometers?

Accepted Answer

500,000–1,000,000 cells/mL

Answer

Most protocols recommend 0.5–1 × 10⁶ cells/mL to minimize coincidence (two cells entering the laser beam simultaneously) and preserve data accuracy.

Question 5

When comparing the MFI of a test sample to a control, the operator must ensure that:

Accepted Answer

Both samples were acquired on the same PMT voltage settings

Answer

MFI comparisons are only valid across samples acquired with identical voltage settings, as changing voltages shifts the fluorescence scale.

(SCYM) Specialist in Cytometry Practice Test

(SCYM) Specialist in Cytometry Practice Test

SCYM Instrument Operation 3