**4.8 Simultaneous banding**

This is the technique that produces simultaneously two types of banding on the same metaphase or on one slide but different metaphases (**Figure 5**). For example, same metaphase ➔ first procedure, G banding ➔ second procedure, C banding OR single slide with different metaphases ➔ first procedure, C banding ➔ second procedure, T banding. Simultaneous banding restricts up to two staining procedures in different or single metaphase and results in precise estimation of chromosomal aberrations [32].

**53**

*Chromosome Banding and Mechanism of Chromosome Aberrations*

The general trend is to pick highly thick and contracted metaphase chromosomes are chosen for banding procedures which gives enough banding patterns for prediction of any kind of aberrations or arrangements within complement, but sometimes it fails also. Therefore, elongated chromosomes (earlier stages of mitotic divisions before reaching metaphase stage) are standardized for banding patterns and prediction of aberrations or arrangements called high resolution banding. Elongated chromosome standardization and preparation could be obtained through synchronization of cell cycle or use of various chromosome anti-contraction reagents through a procedure known as cell cycle synchronization technique. Cell synchronization is a process by which mitotic cells at different stages of cell cycle in culture are brought to the same phase through physical fractionation or chemical blockage or inhibition of DNA synthesis during S-phase. Cell synchrony may be defined as the progression of cells through cell cycle. The possible procedure for high resolution banding pattern are described. Mitotic stages (cultured cells) ➔ cell synchronization by adding chemical reagents ➔ Amethopterin or methotrexate or thymidine or fluorouracil ➔ cultured cells ➔ Blocks DNA synthesis in cultured cells ➔accumulation of cells in S-phase of cell cycle ➔ block released ➔ cell synchrony (large quantities of cells continue their cycle from the same level) ➔ prophase to mid-metaphase range ➔ high number of bands (gives more information as compared to the compact

The technique allows precise localization of break points in chromosomal rearrangements and detection of minute chromosomal alterations that are undetectable

Conventional chromosome banding techniques help us in understanding the patterns associated with chromosomal evolution of a species, speciation processes (formation of a new species) and generation of genetic variability among the species. Similarly, molecular banding techniques such as FISH and GISH provide little more and specific information by causing more differentiation in banding pattern of a chromosome of a particular species. Now, computational analyses (software packages) of the chromosome bands provide maximum information on banding pattern by increasing number of bands which helps to predict the specific and precise result on chromosomal aberrations and arrangements (**Figure 6**). For example, conventional chromosome bands ➔ enough bands for analysis ➔ molecular banding techniques ➔ more bands, more differentiation, more information ➔ computational techniques (software packages) ➔ still more bands, still more differentiation,

Chromosome linearization is an important tool under computational analyses of the chromosome bands which suggest that linear chromosomes will provide maximum number of bands as well as information regarding aberrations or arrangements as compared to the twisted, rounded, curved and overlapped chromosomes. The information obtained from the straight chromosomes will be

*DOI: http://dx.doi.org/10.5772/intechopen.96242*

**4.9 High resolution banding**

metaphase banding) [33, 34].

**5. Chromosome differentiation**

still more information [36].

**6. Chromosome linearization**

by the mid-metaphase banding techniques [35].

**Figure 5.** *Banding techniques for sequential and simultaneous staining.*
