Major advantages

♦ High-density coverage of the human genome with markers.

♦ Small amounts of sample required.

Genomic DNA

Cut with restriction enzyme

Restriction fragments of DNA, length determined by location of recognition sites for restriction enzyme

Gel electrophoresis of DNA fragments

Transfer to nitrocellulose filter by Southern Blot technique

DNA fragments visualized by hybridization to probe

Southern blot analysis.

Combined with micro-dissection of fixed tissue samples, PCR approaches can also study heterogeneity and separate normal and cancerous areas for independent analysis.

Fluorescence in situ hybridization (FISH)

Molecular cytogenetics is a rapidly evolving field; techniques like comparative genomic hybridization (CGH) and interphase cytoge-netics are having major impact on tumour genetics. FISH is a sensitive method for analyzing genetic change in solid tumours, allowing visualization of the genetic make-up of individual cells within their histo-logical context. FISH uses chromosome and region-specific probes to assess and rapidly copy the number and rearrangements of chromo somes and genes. Genetically abnormal cells are detected by an aberrant hybridization pattern in the interphase nuclei (interphase cytogenetics).

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