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Nucleic acid probes also have finite life spans and generally require controlled storage conditions ( e.g ., freezers ) . We found they contained less nucleic acid per particle of virus than did the purified viruses that had been adapted to grow in the chick embryo . Yet prions produce clumps in the brain that are infectious even though no nucleic acid seems to be involved . The term " probe " is described in the specification as a nucleic acid between 10 and 300 base pairs in length which contain specific nucleotide sequences that specifically and preferentially hybridize under predetermined conditions to nucleic acid sequences of bacteria A. Substance records may also have CA index names , synonyms , molecular formulas , alloy composition tables , classes for polymers , protein and nucleic acid sequences , ring analysis data , and structure diagrams , all of which are searchable and displayable .