= Solution
The cytoplasmic viral signal stays predominantly at high molecular size despite longer <nuclease> treatment. \b[The viral <DNA> is protected from digestion, plausibly inside <viral capsids> or assembled particles.] This differs from a nucleosomal ladder: a <capsid> can shield a whole <genome> instead of producing repeated small protected units. Release into the cytoplasm during productive infection makes particle-associated <DNA> a reasonable interpretation.
The virus-negative lane argues against nonspecific hybridization. Protection alone nevertheless does not prove that all detected particles are mature or infectious; an inaccessible compartment or another protective assembly could also shield <DNA>. Comparing intact material with material whose protective envelope or <capsid> has been disrupted would distinguish enclosure from intrinsic <nuclease> resistance of the <DNA>. Fractionation controls would address nuclear contamination. The result is about physical accessibility of viral <DNA>, not a quantitative infectivity assay.
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