Question

2. Some tumor suppressor genes inactivated during multi- step tumorigenesis may be readily identified because of LOH in the chromosomal region carrying them, while others may be difficult to identify in this way. Describe the factors that allow or complicate this identification.

Answer 1

LOH is the loss of heterozygosity. This phenomenon is an event during chromosomal cross over when there is a loss of gene or the surrounding region of the genes. The most powerful techniques to identify those are PCR, Fluorescent in-situ Hybridization (FISH) and marker based assays.

For PCR- They can detect the presence or absence of certain stretch of the gene based on the designed primer. But they can't detect the copy number of certain genes or if there is any single nucleotide polymorphism in the amplified region.

For FISH- We can detect only a specific region of the gene. Although the identification is very specific it is difficult to get the control sample and compare the data. There is always a chance of false positives in this assay.