Biomedical subjects

D S Robertson

Publications and source records attributed to D S Robertson.

At least 37 records · Page 2Linked to original sources

PubMed1993

Cloning of carotenoid biosynthetic genes from maize.

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Alleles↗

PubMed1991

Feedback theory and Darwinian evolution.

Feedback loops can have a significant impact on biological systems that are evolving under Darwinian natural selection. Many of the striking and sometimes bizarre patterns that characterize the evolution of such systems have simple, natural explanations that involve the effects of feedback loops. The two fundamental types of feedback loops, positive and negative, have effects that are radically different: negative feedback tends to produce stability and resistance to change; positive feedback produces instability and even catastrophe. Both types of feedback loops are important in biological systems, and both can produce chaos, whose mathematical complexity often produces strange, beautiful and totally unexpected patterns that have only begun to be explored using the computational capabilities of modern electronic computers. An understanding of the patterns that can result from the effects of feedback loops can produce important new insights into the patterns that mark the evolutionary development of biological systems.

Animals↗

PubMed1991

Cloning of the Mutator transposable element MuA2, a putative regulator of somatic mutability of the a1-Mum2 allele in maize.

The identification of the autonomous or transposase-encoding element of the Mutator (Mu) transposable element system of maize is necessary to the characterization of the system. We reported previously that a transcript homologous to the internal region of the MuA element is associated with activity of the Mutator system. We describe here the cloning of another Mu element, designated MuA2, that cosegregates with Mutator activity as assayed by somatic instability of the a1-Mum2 allele. The MuA2 element has features typical of the transposable elements of the Mutator family, including the 210-bp terminal inverted repeats. Several lines of evidence suggest that MuA2 is an autonomous or transposase-encoding element of the Mu family: (1) MuA2 cosegregates with a genetically defined element that regulates somatic mutability of the a1-Mum2 allele; (2) MuA2 is hypomethylated while most other MuA2-hybridizing sequences in the genome are extensively methylated; (3) the increase of the copy number of MuA2 is concomitant with the increase of regulator elements; (4) MuA2-like elements are found in Mutator lines but not in non-Mutator inbreds. We propose that autonomous or transposase-encoding elements of the Mu family may be structurally conserved and MuA2-like.

Alleles↗

PubMed1989

Chromosome breakage undetectable in active Mu lines of maize.

We have used a set of Mutator-induced mutants of Bz1 to test whether members of the Mutator (Mu) family of maize transposable elements produce broken chromosomes. From our inability to demonstrate the simultaneous loss of two dominant endosperm markers distal to Mu insertions at Bz1 we conclude that either Mu, unlike many elements of the Ds family, does not induce such breaks, or it does so at a very low frequency.

Alleles↗

PubMed1985

Molecular cloning of the a1 locus of Zea mays using the transposable elements En and Mu1.

The a1 locus of Zea mays has been cloned using transposable elements as gene tags. The strategy was to make genomic libraries from maize stocks with a1 mutations induced either by En(Spm) or by Robertson's Mutator-system. These libraries were then screened with either Spm-I8 and En1, for the En-containing mutant, or with Mu1 for the Mu-induced mutation. There are many En and Mu1 hybridizing sequences present in the maize genome, however, by a process of cross-screening of the positives from the two libraries and by molecular analysis of the En-positive clones it was possible to identify clones in both libraries carrying all or part of the a1 gene.

Alcohol Oxidoreductases↗

PubMed1981