= Solution
\b[Latent viral <DNA> has regularly spaced <nucleosome> protection, whereas much of the nuclear viral <DNA> during productive infection lacks that regular protection.] In the latent sample, increasing digestion resolves a ladder of protected fragments, as expected when <micrococcal nuclease> cuts exposed linker <DNA> between <nucleosomes>. In the productive sample, viral signal is lost rapidly into heterogeneous small material rather than accumulating as a comparable ladder. That is consistent with a large pool of newly replicated or otherwise differently packaged viral <DNA> being more accessible.
The total-DNA ladders show that host <chromatin> remains nucleosomal and that the assay can recover protected fragments in each cellular condition. The virus-specific <Southern blot> distinguishes viral <DNA> from this abundant host background, and the uninfected lane controls probe background. The conclusion concerns the dominant detectable viral population: productive cultures can contain both chromatinized templates in <viral latency> and accessible replication products. Absence of a ladder does not establish absence of every <histone> molecule, and differences in <DNA> recovery or <nuclease> accessibility should be considered before assigning a precise fraction of chromatinized <genomes>.
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