A comparison of Southern blot and polymerase chain reaction as techniques to identify loss of DNA heterozygosity in colorectal cancer.

Alterations in the tumour suppressor gene p53 have been found in a wide variety of tumours. The variable number tandem repeat present at the YNZ22 locus is a highly polymorphic marker closely linked to the p53 gene. Examination for loss of heterozygosity at the YNZ22 locus has been carried out by Southern blot or polymerase chain reaction (PCR). A comparison of these techniques shows a 100% concordance rate in normal tissue but a 90.9% rate in tumour tissue. Both false positive and false negative results were obtained. This must be considered in the interpretation of studies using PCR for this purpose.