Abstract
Miller's technique of spreading DNA was applied to monkey cells productively infected with simian adenovirus 7. This permitted the visualization of cellular DNA transcription, both nucleolar and non- nucleolar, and of late transcription and replication of virus. Virus double-stranded DNA, thin fibres with very few nucleosome-like particles, were observed carrying either transcription or replication complexes. In addition, both RNP transcripts and replication forks were found on some virus duplex DNA. Virus single-stranded DNA replicative intermediates were identified on the basis of their increased thickness and contrast which results from the presence of a DNA binding protein.