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R-banding (CAT#: STEM-GT-0013-WXH)

Introduction

Reverse chromosome banding (R-banding) produces a pattern of bands that is the reverse of the Q- and G-banding pattern—i.e., a dark (positive) G-band is a light (negative) R-band and vice versa. In some cases, R-banding is a useful complement to G-banding because some bands (e.g., small negative G-bands) can be more easily detected when they are stained in reverse. R-banding is also useful for visualization of telomeric ends of chromosomes; these ends stain intensely with R-banding and negatively with G-banding.




Principle

The present banding technique is based on the heat denaturation of DNA and proteins. The regions that are stained light pink using the GTG banding are stained darker using the reverse banding. Differential R banding using the fluorescence dye can be stained. Heat denatures the loosely packed AT-rich region but not the GC-rich which stains darker. A differential pattern of chromosome banding reverse to either G or Q banding develops.

Applications

Chromosome identification
Visualization of telomeric ends of chromosomes

Procedure

1. Preheat sodium phosphate buffer to 87° or 88°C in covered Coplin jars in covered circulating water bath.
2. Prewet each air-dried slide of metaphase chromosomes in water and place in sodium phosphate buffer, one slide per jar, 5 to 15 min. Rinse in water.
3. Stain slide 5 to 10 min in Giemsa staining solution. Rinse in water and air dry.
4. View and photograph with bright-field microscope.

Materials

Microscope, Sodium phosphate buffer, Air-dried slides of metaphase chromosomes, Giemsa staining solution

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