Biomedical subjects

N F Weeden

Publications and source records attributed to N F Weeden.

23 records · Page 2Linked to original sources

PubMed1981

Genetic and biochemical implications of the endosymbiotic origin of the chloroplast.

The hypothesis stating that chloroplasts were derived from a photosynthetic procaryote is explored at a genetic and biochemical level. A transfer of genetic material from the endosymbiont to the nucleus of the host cell is proposed along with a corollary argument that the protein products of such transferred genes have remained specific to the chloroplast. This model provides an explanation for the presence of plastid-specific isozymes which are coded by nuclear DNA. It also suggests that the genome of the endosymbiont contributed the information necessary for the biosynthesis of carotenoids and the "essential" amino acids and the assimilation of nitrate-nitrogen and sulfate-sulfur. Animal cells lack these capabilities not because such were lost subsequent to the divergence of the plant and animal lines, but because animal cells did not become host to the appropriate symbionts. Additional implications of this thesis are discussed.

Amino Acids↗

PubMed1980

Isolation of cytoplasmic enzymes from pollen.

The cytoplasmic isozyme of many cytoplasmic-organelle isozyme pairs, as well as other cytoplasmic enzymes in plants, can be readily obtained from pollen by soaking it in an appropriate buffer for 4 hours. Enzymes localized in subcellular organelles appear not to be released during the soaking period, although they are released if the pollen is crushed. The technique is a useful initial step in studies of subcellular localization of enzymes or for obtaining small quantities of cytoplasmic enzymes free of organellar contaminants.

Journal Article↗

PubMed1979

Distinguishing allozymes and isozymes of phosphoglucoisomerases by electrophoretic comparisons of pollen and somatic tissues.

The different electrophoretic patterns of dimeric phosphoglucoisomerases extracted from haploid pollen and diploid somatic tissues of plants may be used to distinguish allozymes and isozymes. The analysis depends on the presence of two alleles at each locus in somatic tissues but only one or the other allele in pollen grains. Consequently, in heterozygotes, heterodimeric allozymes can be identified because they are formed in stems and leaves but not in pollen. The procedure is described in enzymes extracted from the diploid annual plant Clarkia dudleyana, which possesses three gene loci for PGI subunits. Comparison of the electrophoretic patterns of stem and pollen extracts makes it possible in many cases to identify allelic state without breeding tests. The technique also is likely to be useful in the interpretation of zymograms of other multimeric enzymes coded by more than one gene locus.

Alleles↗

PubMedDate not supplied

Chromosomal location of lectin genes indicates they are not the basis of Rhizobium strain specificity mutations identified in pea (Pisum sativum L.).

A lectin gene family is located on linkage group 7 in pea. The lectin genes are arranged as a cluster, with no recombination observed within the multigene family. A lectin-like cDNA clone, pEA207, and eight DNA fragments generated by random priming also were mapped in the region of the lectin genes. None of the known pea mutants altering Rhizobium leguminosarum strain specificity map to this region of the genome, and therefore their altered specificities appear not to be directly produced by mutations in the lectin genes.

Base Sequence↗

PubMedDate not supplied

Molecular marker linkage map for apple.

Linkage maps for two apple clones, White Angel and Rome Beauty, were constructed using isozyme and DNA polymorphisms segregating in a population produced from a Rome Beauty x White Angel cross. The linkage map for White Angel consists of 253 markers arranged in 24 linkage groups and extends over 950 cM. The Rome Beauty map contains 156 markers on 21 linkage groups. The White Angel map was taken as the standard, and we were able to identify linkage groups in Rome Beauty homologous to 13 White Angel linkage groups. The location of several genes not segregating in the Rome Beauty x White Angel population could be determined on the basis of known linkages with segregating markers. Hence, the standard map for apple now contains about 360 markers, with most linkage groups saturated at 10-15 cM. The double pseudotestcross format of the mapping population permitted the comparison of recombination frequencies in male and female parents in certain regions of the genome where appropriate markers were available. The recombination frequencies observed for the approximately 170 cM that were comparable gave no indication that a sex-related difference in recombination rate was characteristic of apple.

Base Sequence↗