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Biochemical Genetics (v.38, #7-8)

Isozyme Diversity in Cassava Cultivars (Manihot esculenta Crantz) by Adriana Gazoli Resende; Pedro Soares Vidigal Filho; Maria de Fátima P.S. Machado (pp. 203-216).

Isoenzyme electrophoresis was used as a method to determine genetic diversity in various M. esculenta cultivars collected in the Southwestern (SW) and Northwestern (NW) regions of the State of Parana, in the South region of Brazil, and in cultivars produced at the Agronomic Institute of Campinas (IAC), S~ao Paulo State, Southeastern region of Brazil. The cultivars have been maintained by vegetative propagation for 5 years and are useful in production programs. A total of 28 loci in the acid phosphatase (ACP; EC 3.1.3.2), esterases (EST; EC 3.1.1.1), malate dehydrogenase (MDH; EC 1.1.1.37), and shikimate dehydrogenase (SKDH; EC 1.1.1.15) isozymes was analyzed. The proportion of polymorphic loci for NW, SW, and IAC cultivars was 57.14, 50.0, and 53.6%, respectively. Genetic diversity calculated by Nei's genetic identity (I) showed high I values for the three M. esculenta subpopulations. The high degree of polymorphism expressed by cassava cultivars is highly relevant to stimulate breeding programs with M. esculenta species.

Keywords: cassava; isozyme polymorphisms; esterases; malate dehydrogenases; shikimate dehydrogenases; acid phosphatase; Manihot esculenta.

A Highly Polymorphic Plasma Protein Locus in Brown Trout (Salmo trutta L.) Populations from Portugal by A. Antunes; N. Ferrand; P. Alexandrino (pp. 217-226).

Genetic polymorphism of an unidentified plasma protein (PX) is described for the first time in Salmo trutta (L.) by means of isoelectric focusing. The analysis of 414 individuals from different geographic origins in Portugal allowed the identification of nine alleles. Heterozygosity in natural populations is generally above 0.60, thus giving similar values to those reported for brown trout microsatellite loci. Substructuring of Portuguese brown trout is evident between northern and southern basins. Genetic affinities between the southernmost rivers and the hatchery stock were detected, suggesting the existence of recent stocking influences.

Keywords: plasma protein; polymorphism; isoelectric focusing; brown troutSalmo trutta ; salmonids.

Telomeres in Warm-Blooded Vertebrates Are Composed of GC-Rich Isochores by P. Perani; S. Cacciò; S. Saccone; L. Andreozzi; G. Bernardi (pp. 227-239).

We have hybridized the vertebrate telomeric sequence (TTAGGG)n on DNA compositional fractions from 13 mammalian species and 3 avian species, representing 9 and 3 orders, respectively. Our results indicate that the 50- to 100-kb fragments derived from telomeric regions are composed of GC-rich and GC-richest isochores. Previous works from our laboratory demonstrated that single-copy sequences from the human H3 isochore family (the GC-richest and gene-richest isochore in the human genome) share homology with compositionally correlated compartments of warm-blooded vertebrates. This correlation suggested that the GC-richest isochores are, as in the human genome, the gene-richest regions of warm-blooded vertebrates' genome. Moreover, this evidence suggests that telomeric regions are the most gene-dense region of all warm-blooded vertebrates. The implications of these findings are discussed.

Keywords: isochores; GC composition; telomeres; warm-blooded vertebrates

Absence or Reduction of Carbonic Anhydrase II in the Red Cells of the Beluga Whale and Llama: Implications for Adaptation to Hypoxia by Hong Yang; David Hewett-Emmett; Richard E. Tashian (pp. 241-252).

Carbonic anhydrase (CA) expression was examined in the red cells of two mammals that have adapted to low oxygen stress: the llama, which has adapted to high altitudes, and the beluga (or white) whale, which routinely dives for extended periods. Immunodiffusion analyses of their Hb-free hemolysates and partial amino acid sequencing of their HPLC-separated nonheme proteins indicate that the low-activity CA I isozyme is the major nonheme protein in erythrocytes of both the beluga whale and the llama. The high-activity CA II isozyme was not detected in the whale red cells but was present at low levels in erythrocytes of the llama. These results suggest that the absence or decrease in the expression of the high-activity CA II isozyme may be advantageous under hypoxic conditions.

Keywords: hypoxia; red cell carbonic anhydrases; beluga whale; llama

Genome Organization and Phylogenetic Distribution of a Novel Family of Ancient Murine Endogenous Proviruses with Evidence for Transposition-Mediated Proliferation by Edmund J. Zimmerer; Jennifer Carneal; James B. Robertson; Mehmet Ozturk; Suzie Cardiff; Manlin Luo (pp. 253-265).

A new family of murine endogenous proviruses (VL6.0) is described here. The intact provirus is near 6 kb in length and shows a genomic organization of 5" LTR, gag, pol, env, and 3" LTR. The primer binding site (PBS) is that of a tRNA^gly. The lack of functional open reading frames and occurrence of significant gaps in most, if not all, members of this group show it to be ancient. Our estimate of copy number per haploid genome is 30+. Members of this group have been isolated from Mus musculus domesticus, M. m. casteneus, M. m. hortulanus, M. caroli, and M. spretus. The occurrence of these sequences throughout such diverse members of the genus Mus may indicate that the date of the original infection predated the divergence of the extant Mus lineages at around 2.5 million years ago. Analysis of gap (deletion/insertion) patterns indicates that these sequences may have proliferated within the Mus genome by a mechanism of reverse transcriptase-mediated transposition. As yet, there are no closely related murine retroviruses described. The closest mammalian retrovirus based on sequence similarity is from the miniature swine (Sus scrofa).

Keywords: ancient endogenous provirus; evolution; retrotransposition

Inheritance of Allozyme Loci in Bombina: Second Linkage Group Established by Sebastian Hofman; Jacek M. Szymura (pp. 267-274).

Segregation and linkage relationship of nine allozyme loci, which are fixed for alternative alleles in the European fire-bellied toads, Bombina bombina and B. variegata,were studied using artificial F₁ hybrids to obtain backcross and F₂ progeny. Alleles coding for electromorphs at nine loci (Ldh-1, Mdh-1, Idh-1, Ck, Ak, Gpi, Aat-1, Np, and G6pd)showed Mendelian ratios. Two of the loci, Ak and G6pd, were found to be closely linked (2 cM apart); the other loci assorted independently.

Keywords: allozymes: Amphibia; electrophoresis; inheritance; fire-bellied toad; linkage group

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Biochemical Genetics (v.38, #7-8)

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Biochemical Genetics (v.38, #7-8)