Loss of heterozygosity in tumor cells

Usually, in about half of the individuals who are
heterozygous for DNA markers at the tumor
suppressor gene locus of interest, the loss of one
allele (event 2) can be demonstrated by Southern
blot analysis. In contrast to normal somatic
cells (blood), tumor cells contain only one allele
(loss of heterozygosity, LOH). The remaining allele
carries the mutation. Thus, the mutant allele
can be identified by demonstration of LOH.
LOH is useful in diagnosis as an indication of the
existence of a tumor suppressor gene.