central dogma of molecular biology. The central dogma states that genetic information passes from DNA to protein in a one-way information pathway. It indicates that genotype codes for phenotype but phenotype cannot code for genotype. We now realize, however, that the central dogma is an oversimplification. In addition to the three general information pathways of replication, transcription, and translation, other transfers may take place in certain organisms or under special circumstances, including the transfer of information from RNA to DNA, (in reverse transcription) and the transfer of information from RNA to RNA (in RNA replication; see Figure 10.16). Reverse transcription takes place in retroviruses and in some transposable elements; RNA replication takes place in some RNA viruses (see Chapter 8).

(a) Hairpin


The genetic information of DNA resides in the base sequence. When DNA replicates, the two strands separate, and each strand serves as a template on which a new strand is synthesized. Three principle pathways transfer genetic information: genetic information can pass from DNA to DNA through replication, from DNA to RNA through transcription, and from RNA to protein through translation.



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