A COMPARISON OF SOUTHERN BLOT AND POLYMERASE CHAIN REACTION AS TECHNIQUES TO IDENTIFY LOSS OF DNA HETEROZYGOSITY IN COLORECTAL CANCER

Abstract
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.