Northern blot analysis of TCRβ germline transcription. (A) Map of the D-J-C region of the TCRβ locus showing the location of the Dβ1 probe used in Northern analysis, as well as the Cβ1 probe used to isolate cDNA clones depicted in Fig 2. (B) Northern blot using Dβ1 probe to detect germline TCRβ transcripts in total RNA from the p5424 and p4980 cell lines and from thymocytes from either Rag-2–deficient or normal mice as indicated. Lane loading was equivalent as determined by ethidium bromide staining. The position of the 28S and 18S ribosomal RNA bands are indicated by arrows.