Early differential tissue expression of transposon-like repetitive DNA sequences of the mouse.

Another family of long moderately repetitive and dispersed sequences has been identified in the mouse genome. These sequences have a transposon-like structure. A 6-kilobase RNA transcript is detected in undifferentiated embryonal carcinoma cell lines but not in any of the differentiated cell types tested. By R-loop formation, the RNA is colinear with a DNA fragment from a randomly selected genomic clone.