Multiple choice

The steps followed in Gram’s staining of microorganisms are P. Washing with neutral organic solvent Q. Counter staining with a contrast dye R. Staining with basic dye S. Fixing the colour with a suitable mordant Identify the CORRECT sequence.

  1. Q $\rightarrow$ S $\rightarrow$ R $\rightarrow$ P
  2. P $\rightarrow$ Q $\rightarrow$ R $\rightarrow$ S
  3. Q $\rightarrow$ P $\rightarrow$ S $\rightarrow$ R
  4. R $\rightarrow$ S $\rightarrow$ P $\rightarrow$ Q
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Gram staining follows a specific sequence: first stain with a basic dye like crystal violet (R), fix with a mordant like iodine (S), decolorize or wash with an organic solvent like alcohol (P), and finally counterstain with a contrast dye like safranin (Q). Thus, the correct operational order is R, S, P, Q.

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