Biomedical subjects

B Dixon

Publications and source records attributed to B Dixon.

At least 19 recordsLinked to original sources

PubMed1992

A nematode hemoglobin gene contains an intron previously thought to be unique to plants.

Hemoglobin genes from plants and animals both have a characteristic chromosomal organization. Plant hemoglobin genes contains a unique intron inserted into the heme-binding domain of exon 2. This intron has not been previously reported in animal globin genes, and its loss was hypothesized to have occurred early in the evolution of hemoglobins. We report here a unique six-intron, seven-exon internally duplicated nematode hemoglobin gene that contains an intron equivalent to the plant central intron in its first repeat. This nematode hemoglobin gene has lost both the central and the normal third intron in its second repeat. The nematode globin also contains a unique intron between its secretory peptide leader sequence and its coding sequence, which is absent in other extracellular invertebrate globin genes. Possible models to explain the head-to-tail duplication of this gene are discussed.

Amino Acid Sequence↗

PubMed1992

Isolation of a putative retrovirus pol gene fragment from trout.

1. A 220 bp DNA fragment was obtained from three different species of salmonids during PCR analysis using a primer sequence based on human beta-2 microglobulin. All of the 220 bp fragments showed strong homology to each other. 2. Several of the DNA sequences also contained protein reading frames. Searching DNA and protein databases revealed significant homology to a segment of the pol gene (reverse transcriptase) from various retroviruses. Phylogenetic analysis at both the DNA and the protein levels showed clustering of the fish sequences and the closest viral sequence was the Moloney murine leukaemia virus (MoMuLV). Southern analysis indicated that there are several copies of the gene dispersed throughout the salmonid genome. 3. Preliminary results suggest that these sequences may be unique to the family Salmonidae. This would suggest that this retrovirus was incorporated in the DNA of an ancestral salmonid prior to the evolution and divergence of this family of fish.

Amino Acid Sequence↗

PubMed1992

Did the ancestral globin gene of plants and animals contain only two introns?

All vertebrate globin genes contain two introns, while plant globin genes contain three. It is widely thought that the plant gene structure reflects the structure of the primordial globin gene and that a common ancestor of all animals lost the central intron shortly after the divergence of plants and animals more than one billion years ago. The recent discovery of a discordant central intron in some animal globin genes suggests that this model is incorrect. We propose that the typical vertebrate two-intron gene structure is the primordial eukaryotic form, and that following the divergence of plants and animals, a common ancestor of plants gained a central intron in the globin gene.

Amino Acid Sequence↗

PubMed1991