A well-documented case of partial thyroidal iodide transport deficiency in a patient with E18p- is described. It is suggested that several genes regulating various steps of intrathyroidal iodide utilization are localized in this area of chromosome E18.

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SummaryThe concepts of Chronon and Chronaxy of Gedda are discussed in the light of recent biochemical-genetic knowledge. It is proposed that the term «positive chronaxy» and «negative chronaxy» be employed to designate the period during which a gene is in active and inactive state, respectively. Other terms proposed are «recurrent positive chronaxy», «recurrent negative chronaxy» and « uncoordinated chronaxy». It is pointed out that the different chronaxy states of genes may be subject to modification by certain agents. If a given agent is able to change a gene from a negative chronaxy state into positive chronaxy state, the gene toward this agent behaves as being in a «conditionally negative chronaxy state». In the same sense, we can speak also of a «conditionally positive chronaxy state» of a gene. It is proposed that mutations facilitating malignant transformation of cells can, theoretically, occur in both the active and inactive segments of the DNA. If active segments of the DNA are affected, i.e. those in positive chronaxy state, the effects of such mutations would be expressed immediately. If, however, genes in negative chronaxy state have similar mutations, their effect would be expressed only if these genes become activated by some agents, either physiological or unphysiological. Malignancies facilitated by hormonal inbalance may represent instances or mutated gene activation by physiological agents while tumors caused by carginogenic substances with a structure resembling steroid hormones could be examples of gene activation by unphysiological agents.

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