Southern blot analysis of DNA extracted from paraffin wax-embedded tissue.

Genetic analysis of multi-generation families using RFLP is often incomplete because fresh tissue is not available for the isolation of DNA. However, in many instances archival material exists, usually formalin-fixed in paraffin blocks. Procedures have been described for extracting DNA from such specimens. Many parameters affect the quality of the DNA eventually extracted and this in turn determines whether the DNA can be successfully digested with restriction enzymes and probed (Dubeau et al., 1986; Warford et al., 1988). In essence, the procedures followed at the time of fixation largely determine whether archival material will yield useful results. We have re-examined the effect of varying the fixation time but, more importantly, we have assessed the validity of RFLP results obtained from fixed tissue.