# DBT JRF 2022 — Question 136

Exam: DBT JRF 2022 · Section: B · Topic: Cell Biology › Cell Cycle Analysis & Flow Cytometry · Difficulty: Medium

## Question

Which one of the following cell separation techniques allows cells from different stages of the cell cycle to be separated simultaneously with minimal perturbation to their physiology?

## Options

- **A.** counterflow centrifugal elutriation
- **B.** fluorescent activated cell sorter
- **C.** size exclusion chromatography
- **D.** ultracentrifugation

## Answer

Option A

## Explanation

Counterflow centrifugal elutriation for cell cycle synchronisation: Counterflow centrifugal elutriation (CCE) separates cells based primarily on SIZE and to a lesser extent on DENSITY: Principle: • Cells are pumped into a rotor chamber against centrifugal force. • By varying the flow rate (counterflow), cells of different sizes reach equilibrium at different positions in the chamber. • Eluting fractions at increasing flow rates separates cells by size. Advantages over other methods: • Continuous separation: can isolate multiple cell cycle stages simultaneously from one run. • Minimal perturbation: no drugs (unlike hydroxyurea or nocodazole blocks), no temperature shock — cells remain physiologically normal. • High yield and viability. Comparison with alternatives: • FACS: uses fluorescent markers; can separate by cell cycle stage but requires labelling. • SEC: not applicable for live cell separation in liquid suspension at scale. • Ultracentrifugation: separates by density; not appropriate for living cells without osmotic stress. Answer: Counterflow centrifugal elutriation separates cells by size without chemical perturbation, allowing simultaneous isolation of multiple cell cycle stages.

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