Structural variants of the alpha-fetoprotein gene in different inbred strains of rat

Two structural variants of the rat alpha-fetoprotein (AFP) gene have been detected in different inbred strains of rats by EcoRI or HindIII restriction enzyme cleavage of cellular DNA, agarose gel electrophoresis and Southern blot hybridization using 32P-labeled cloned rat AFP cDNA probes. The type I AFP gene variant is characteristic of the Sprague-Dawley strain, and type II is found in Buffalo rats. These variants appear to represent two different allelic forms of the rat AFP gene since they are inherited in a normal Mendelian fashion when Sprague-Dawley and Buffalo rats are crossed. The mapping results suggest that the two allelic variants differ from each other by multiple cleavage site variations (base pair substitutions) and by an insertion or deletion of DNA sequences. An extensive sequence variation appears to exist between the two forms of the rat AFP gene; we have estimated that as much as 2.7% of the nucleotides in this region vary between the two alleles.