Triplet Coding Dictionary

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Triplet Coding Dictionary
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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.
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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.
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An example of the triplet binding assay. The UUU
triplet acts as a codon, attracting the
complementary tRNAphe anticodon AAA.
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The conversion of di-, tri-, and tetranucleotides
into repeating copolymers. The triplet codons
that are produced in each case are shown.
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Triplet Coding Dictionary
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TRANSCRIPTION MAKING RNA
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The Early Stages of Transcription in Prokaryotes
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template binding at the -10 site involving the
sigma subunit of RNA polymerase and subsequent
initiation of RNA synthesis.
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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.
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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.
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Intervening Sequences in Various Eukaryotic Genes
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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.
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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.
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