AbstractThis report provides a more rigorous proof of previous findings that the RNA transcribed in vitro from the chromatins of different organs shows different sequence specificities. Here the particular case of the globin gene is considered for a comparison of embryonic mouse liver chromatin and mouse brain chromatin using the reverse transcriptase cDNA copy of globin 9S mRNA as a definitive probe. It can be shown that globin sequences are transcribed in vitro from embryonic liver chromatin and not brain chromatin. This specificity in liver chromatin can be reconstituted after dissociation of the structural elements of the chromatin. It can be shown that the non‐histone protein fraction of liver chromatin can confer specificity for the transcription of globin sequences from brain chromatin which otherwise lacks this ability.Preliminary results are described with the Friend cell system, in which haemoglobin synthesis can be induced in vitro in the presence of dimethylsulphoxid