Question

Which of the following dyes are used for staining chromosomes?
(A) Giemsa
(B) Quinacrine
(C) Eosin Y
(D) Methylene blue
Choose the correct answer from the options given below:

• A. (A), (B) and (D) only
• B. (A) and (B) only
• C. (A), (B) and (C) only
• D. (A), (B), (C) and (D)

Hint:

Remember the two main types of chromosome banding:
- G-banding uses Giemsa dye.
- Q-banding uses Quinacrine dye (fluorescent).
This mnemonic makes it easy to remember the two primary cytogenetic stains.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Karyotyping and cytogenetic studies rely on chromosome staining techniques to visualize and identify chromosomes under a microscope.
Different staining techniques yield distinct banding patterns (like G-banding or Q-banding) that help identify individual chromosomes and structural abnormalities.

Step 2: Detailed Explanation:
The dyes most specifically and commonly used for classical chromosomal staining and banding are:
- Giemsa Stain (A): Used in G-banding, which is the most widely used cytogenetic method.
Giemsa specifically stains AT-rich heterochromatic regions intensely, producing dark bands, while gene-rich euchromatic regions appear light.
- Quinacrine (B): Used in Q-banding.
Quinacrine is a fluorescent intercalating agent that binds to DNA and exhibits differential fluorescence, yielding bright bands in AT-rich regions.
- Eosin Y (C) is primarily a cytoplasmic counterstain used with hematoxylin in tissue histology.
- Methylene blue (D) is a general basic stain used for simple staining of bacteria and dead cells, but is not a standard cytogenetic dye for diagnostic chromosome banding.
Therefore, only Giemsa and Quinacrine are standard, specific chromosome staining/banding dyes.

Step 3: Final Answer:
The dyes used for staining chromosomes are (A) and (B) only.