Banding

Question.

200. Which of the following procedures are wsed as routine technique for karyotyping using light microscopy ?

1. C- banding

2. G- banding

3. Q- banding

4. B-rd V- staning

Answer

2. G- banding

Reference

Robbins Pathologic Basis Of Disease 6^th Edition Pg-165

Quality

Spotter

Status

New

QTDF

Robbins

Discussion

Karyotyping (karyo=nut + typing) is the process of arresting the chromosomes in metaphase state , where they are arranged in pairs and take the shape of X connected at the centromere and are arranged in decreasing order of length.

The chromosomes are stained and by this the Structure of the Chromosome is Studied(See another Question on RFLP in this book)

Banding	Name	Remarks
G	Giemsa	Most commonly used
Q	Quinacrine
C	Constitutive Centromere	Shows constitutive heterpchromatin
R	Reverse	Opposite to G Banding

Explanation

1. C- banding is preferential staining of constitutive Hemochromatin

2. G- banding uses Giemsa

3. Q- banding uses Quinacrine and uv light

4. B-rd V- staning uses uv light

Comments

About G Banding

· Purpose:

o To stain metaphase chromosomes with Giemsa or Leishman's stain to elicit a banding pattern throughout the chromosome arms, designated G-Bands. This G-Banding technique requires a chromosomal pretreatment step of trypsin to induce chromosome bands.

· Time required:

o 30-60 minutes

· Special Reagents:

o Leishman stain (Baxter, cat. no. S7710-27)

o Gurr Buffer Tablets (Biomedical Specialties, cat. no.33199)

Tips

· The patterns of G- and Q- bands on a chromosome are sufficiently unique to allow that chromosome's unambiguous identification. Best banding is obtained with prophase chromosomes since these have not yet fully condensed

· An arrayed set of banded chromosomes is called a karyotype and can be used to screen for chromosome rearrangements.

· G-, Q-, and R- bandings are not observed with plant chromosomes.

· Banding patterns appear related to base composition and chromosome loop structure.

· Additional types of banding are also used. For example: N-banding which corresponds to locations of GARn triplet repeats in wheat and barley