Triplet Coding Dictionary. Crick et al. 1950s, T4 phage studies:
The effect of frameshift mutations on a DNA sequence with the repeating triplet sequence GAG. (a) The insertion of a single nucleotide shifts all subsequent triplet reading frames. (b) The insertion of three nucleotides changes only two triplets, but the frame of reading is then reestablished to the original sequence.
The reaction catalyzed by the enzyme polynucleotide phosphorylase. Note that the equilibrium of the reaction favors the degradation of RNA but can be “forced” in the direction favoring synthesis.
An example of the triplet binding assay. The UUU triplet acts as a codon, attracting the complementary tRNAphe anticodon AAA.
The conversion of di-, tri-, and tetranucleotides into repeating copolymers. The triplet codons that are produced in each case are shown.
template binding at the -10 site involving the sigma subunit of RNA polymerase and subsequent initiation of RNA synthesis.
Posttranscriptional RNA processing in eukaryotes. Heterogeneous nuclear RNA (pre-mRNA) is converted to mRNA, which contains a 5’-cap and a 3’-poly-A tail. The introns are then spliced out.
An interpretive drawing of the hybrid molecule (heteroduplex) formed between the template DNA strand of the chicken ovalbumin gene and the mature ovalbumin mRNA. Seven DNA introns, labeled A through G, produce unpaired loops.
Splicing mechanism of pre-rRNA involving group I introns that are removed from the initial transcript. The process is one of self-excision involving two transesterification reactions.
A model of the splicing mechanism involved with the removal of an intron from a pre-mRNA. Excision is dependent on various snRNAs (U1, U2,..., U6) that combine with proteins to form snurps, which are part of the spliceosome. The lariat structure in the intermediate stage is characteristic of this mechanism.