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PubMed1981

Possibility of genetic coding of amino acid sequences by coherent electronic states in nucleotide chains.

The concept of coherent electronic states and coherent interactions in supramolecular structures is applied to the process of genetic information coding and its transcription from DNA to mRNA. A new genetic code is proposed based on the assumption of coherent electron states in linear chains of nucleotide bases. A new interpretation of codon equivalency (redundancy) is given. The number of existing amino acids is derived from the optimalization principle applied to the physical system storing the genetic information in the new code. The proposed code uses a variable number of positions or nucleotide bases along the DNA-mRNA structure to code a single amino acid in a protein. The average of this variable number must be equal to the base of natural logarithms (e = 2.7 . . .) in order to minimize the number of nucleotides required to code a sequence of amino acids.

Amino Acid Sequence↗

PubMed1988

Evolutionary implication of genetic code deviations.

We formulate the following hypothesis: Life's origin may have occurred during the lower Archaean at a time when the environmental temperature was higher than it is at present. Preliminary consequences of this hypothesis are studied from the point of view of molecular evolution. We restrict our attention to implications regarding the genetic code. We conclude that alternative assignment of termination codons may be understood in terms of: (a) the elevated temperatures to which the progenote may initially have been exposed; and (b) the subsequent response of its genome to the opportunity provided by the eventual loss of hyperthermal genetic expression during a thermal transition (TT) period, which was triggered off by the evolution of the dynamic Earth.

Biological Evolution↗

PubMed1980

[Use of the degeneracy of the genetic code by selective pressure to cut up genes of procaryote genomes].

The DNA sequences of three bacteriophages are analysed in order to localise those parts coding for a protein. A weak stability on the DNA molecule allows us to characterize the beginning and the end of genes. A survey of the codons used shows that the cause for this weak stability is the systematic use of A-T bases in third position, which is made possible by the degeneracy of the genetic code.

Bacteriophage phi X 174↗

PubMed1990

The genetic code of a squid mitochondrial gene.

Cytochrome oxidase subunit I gene of a squid (Mollusca), Doryteuthis mitochondrial genome was sequenced. Comparison with the nucleotide sequence and the deduced amino acid sequence of other animal mitochondria suggests that the squid mitochondria has a variation in the genetic code; UGA codes for tryptophan, AUA for methionine and AGA/G for serine. This situation is similar to the case of Drosophila or Ascaris mitochondria.

Amino Acid Sequence↗

PubMedDate not supplied

Drosophila melanogaster mitochondrial DNA, a novel organization and genetic code.

The sequence of a 4,869 base-pair fragment of Drosophila melanogaster mitochondrial DNA is presented. It contains genes for cytochrome oxidase subunits I, II and III, ATPase subunit 6 and six tRNAs together with two unassigned reading frames. The gene organization differs from that of mammalian mitochondrial DNAs. Evidence is provided for a genetic code in which AGA codes for serine and the quadruplet ATAA is used in initiation of translation.

Amino Acid Sequence↗

PubMed1991

Selenoprotein synthesis: an expansion of the genetic code.

A number of enzymes employ the unusual amino acid selenocysteine as part of their active site because of its high chemical reactivity. Selenocysteine is incorporated into these proteins co-translationally: biosynthesis occurs on a specific tRNA and insertion into a growing polypeptide is directed by a UGA codon in the mRNA. In E. coli, this requires a specific translation factor. Selenocysteine thus represents a unique expansion of the genetic code.

Animals↗

PubMed1989