Restriction fragment length polymorphisms in the rat N-ras and retinoblastoma genes: their identification and...

We have observed restriction fragment length polymorphisms for the N-ras and retinoblastoma (Rb) genes between rat strains that are susceptible or resistant to induction of pituitary tumors by diethylstilbestrol (DES). Thirteen other proto-oncogenes tested displayed the same restriction patterns between all samples. The N-ras polymorphism is observed with more than one restriction nuclease and the N-ras and Rb polymorphisms are not a result of DES treatment. The N-ras polymorphism is inherited in a Mendelian fashion and there appear to be two separate loci in the rat genome that are detected by the N-ras probe. For both the N-ras and Rb genes there is an 'extra' fragment in the tumor-resistant animals that is not seen in the susceptible rats. These polymorphisms may indicate regions of the genome that play a role in determining susceptibility to pituitary tumors or any of a number of other chemically induced tumors.