An allelism test for quantitative trait genes

Analytical modeling has been used to test assumptions on the mode of inheritance of a quantitative trait in the course of diallel crossing between pure lines that are sufficient for adequacy of a simple regression model. This model frequently proved to be adequate in analysis of numerous data on diallel crossings of wheat and maize. An allelism test for quantitative trait genes has been suggested. Computer simulation has been used to estimate the effect of random experimental errors and deviations from the model assumptions.     

QTL marking of duration of the period up to winter wheat heading

Duration of the period up to heading of 107 winter wheat cultivars of different origin has been studied. The most contrast for analyzed character cultivars, as well as F2 Omskaya ozimaya/Numbu Komugi individual plants were investigated with SSR-PCR methods to reveal DNA-markers for QTL of heading temps. Two loci Xgwm512 and Xgwm429 have been revealed to explain 19.3% (part of influence of the first locus--8.9%, of the second 10.4%) differences induration of the period up to heading of the F2 individuals in field conditions.     

Quantitative trait loci for sucrose, starch, and hexose accumulation before heading in rice.

We studied the storage of sucrose, starch, and hexose before heading in rice (Oryza sativa L.) plants by quantitative trait locus (QTL) analysis with a population of backcross inbred lines (BILs) of japonica cv. Nipponbare x indica cv. Kasalath. Carbohydrates are accumulated in the rice plant before heading and are translated to the panicle after heading. A higher capacity for accumulation is thus a main target for improvement in yield. The form of carbohydrate (sucrose, starch, or hexose) differs depending on the organ in which it is stored. There was no correlation between starch and sucrose or hexose contents in BILs, and the positions of QTLs controlling starch differed from those for sucrose and hexose accumulation. These results suggest that the genetic control of accumulation differs between starch and sugars. QTLs that control the ratio of sucrose to starch content were detected, suggesting the existence of a mechanism(s) that determines this ratio. On chromosome 1, sucrose-phosphate synthase 1, the key enzyme in sucrose synthesis was close to the peaks of the likelihood odds ratios in QTLs for sucrose or hexose content. These results suggest that SPS1 is related to conversion of carbohydrate to sucrose as accumulated form in a plant before heading.     

A transposable element in diverse corn lines,Ubiquitous (Uq): allelism test

Since the discovery of the Uq transposable element system in the early 1980s, studies of Uq distribution have shown that Uq is pervasive in genetic stocks and corn populations including BSSS, the Illinois oil and protein lines, ‘Lancaster’, ‘Jarvis’ and several others. The assumption made was that Uq might have provided the variation that has contributed to maize breeding progress. Of the several inbreds tested in previous studies, only IaI159, one of the contributors to BSSS, contained an active Uq. The main question posed in our experiments was that of chromosomal location(s), or allelic relationships, of active Uq elements in diverse corn populations. Results showed that these Uq elements are allelic, linked or independent, though most found from corn populations show quite distant or independent linkage relationships with each other. The lack of a linear linkage map among these Uq elements may be interpreted to have resulted from transposition events and this might have led to the differentiated instability of an individual Uq element that was found to be variable. Other questions also discussed relate to the origin of Uq elements in corn populations and their role(s) in plant breeding.     

Micronucleus test applied in patients with acute leukemia, before and at different intervals during the cytostatic treatment

The micronucleus test was applied in a group of 36 patients with malignant disease of the blood (acute lymphoblastic leukemia, ALL, and acute non-lymphocytic leukemia, ANLL) in order to evaluate to what extent it may be relevant for the efficiency of the cytostatic treatment. To this end, the test was applied at the onset of the disease (when diagnosed) and at different intervals after initiating the cytostatic therapy. Determination of the incidence of micronucleated cells and immature cells (blasts) at the two moments of the study established a correlation between the frequency of micronucleated cells and blast cells, the response to the anticancerous treatment and survival duration, the data obtained reflecting the prognostic value of the test in some malignant hemopathies.     

The distribution of lethal allelism in finite populations

It is shown that, under certain conditions, the distribution of lethal allelism in equilibrium populations is independent of the fitness of heterozygotes. For these conditions, an expression for the over-generation variance of allelism is given.     

On origin of genetic code and tRNA before translation

Background  

Synthesis of proteins is based on the genetic code - a nearly universal assignment of codons to amino acids (aas). A major challenge to the understanding of the origins of this assignment is the archetypal "key-lock vs. frozen accident" dilemma. Here we re-examine this dilemma in light of 1) the fundamental veto on "foresight evolution", 2) modular structures of tRNAs and aminoacyl-tRNA synthetases, and 3) the updated library of aa-binding sites in RNA aptamers successfully selected in vitro for eight amino acids.     

Characterization of the acclimation period before anaerobic dehalogenation of halobenzoates

The acclimation periods prior to detectable dehalogenation of halogenated benzoates in anaerobic lake sediments ranged from 3 weeks to 6 months. These acclimation periods were reproducible over time and among sampling sites and were characteristic of the chemical tested. The lengthy acclimation period appears to represent an induction phase in which little or no aryl dehalogenation is observed, followed by an exponential increase in activity typical of an enrichment response. Continuous growth from the time of the first exposure to the chemical is inconsistent with the extremely low per-cell activities estimated for the early days of the acclimation period and the fact that the dehalogenation yields no carbon to support microbial growth. The finding of a characteristic acclimation time for each chemical argues against nutritional deficiency, inhibition, or predation as an explanation for this phase of metabolism, while the reproducibility of the findings with time and space and among replicates argues against genetic changes as the explanation. The acclimation times did correlate with the eventual dehalogenation rates. This may reflect the general energy limitations in the anaerobic communities and suggests that those chemicals with faster dehalogenation rates provide more energy for the induction and growth phases of the active population.     

Ancient allelism at the cytosolic chaperonin-alpha-encoding gene of the zebrafish

The T-complex protein 1, TCP1, gene codes for the CCT-alpha subunit of the group II chaperonins. The gene was first described in the house mouse, in which it is closely linked to the T locus at a distance of approximately 11 cM from the Mhc. In the zebrafish, Danio rerio, in which the T homolog is linked to the class I Mhc loci, the TCP1 locus segregates independently of both the T and the Mhc loci. Despite its conservation between species, the zebrafish TCP1 locus is highly polymorphic. In a sample of 15 individuals and the screening of a cDNA library, 12 different alleles were found, and some of the allelic pairs were found to differ by up to nine nucleotides in a 275-bp-long stretch of sequence. The substitutions occur in both translated and untranslated regions, but in the former they occur predominantly at synonymous codon sites. Phylogenetically, the alleles fall into two groups distinguished also by the presence or absence of a 10-bp insertion/deletion in the 3' untranslated region. The two groups may have diverged as long as 3.5 mya, and the polymorphic differences may have accumulated by genetic drift in geographically isolated populations.     

A test of the coordinated expression hypothesis for the origin and maintenance of the GAL cluster in yeast

Metabolic gene clusters--functionally related and physically clustered genes--are a common feature of some eukaryotic genomes. Two hypotheses have been advanced to explain the origin and maintenance of metabolic gene clusters: coordinated gene expression and genetic linkage. Here we test the hypothesis that selection for coordinated gene expression underlies the clustering of GAL genes in the yeast genome. We find that, although clustering coordinates the expression of GAL1 and GAL10, disrupting the GAL cluster does not impair fitness, suggesting that other mechanisms, such as genetic linkage, drive the origin and maintenance metabolic gene clusters.     

Inheritance and allelism tests of Raiden soybean for resistance to soybean mosaic virus

The gene symbol Rsv2 was previously assigned to the gene in the soybean [Glycine max (L.) Merr.] line OX670 for resistance to soybean mosaic virus (SMV). The Rsv2 gene was reported to be derived from the Raiden soybean (PI 360844) and to be independent of Rsv1. Accumulated data from our genetic experiments were in disagreement with this conclusion. In this study, Raiden and L88-8431, a Williams BC5 isoline with SMV resistance derived from Raiden, were crossed with two SMV-susceptible cultivars to investigate the mode of inheritance of SMV resistance in Raiden. They were also crossed with five resistant cultivars to examine the allelomorphic relationships of the Raiden gene with other reported genes at the Rsv1 locus. F1 plants, F2 populations, and F2-derived F3 (F2:3) lines were tested with SMV strains G1 or G7 in the greenhouse or in the field. The individual plant reactions were classified as resistant (R, symptomless), necrotic (N, systemic necrosis), or susceptible (S, mosaic). The F2 populations from R x S crosses segregated in a ratio of 3 (R + N):1 S and the F2:3 lines from Lee 68 (S) x Raiden (R) exhibited a segregation pattern of 1 (all R):2 segregating:1 (all S). The F2 populations and F2:3 progenies from all R x R crosses did not show any segregation for susceptibility. These results demonstrate that the resistance to SMV in Raiden and L88-8431 is controlled by a single dominant gene and the gene is allelic to Rsv1. The heterozygous plants from R x S and R x N crosses exhibited systemic necrosis when inoculated with SMV G7, indicating a partial dominance nature of the resistance gene. Raiden and L88-8431 are both resistant to SMV G1-G4 and G7, but necrotic to G5, G6, and G7A. Since the resistance gene in Raiden is clearly an allele at the Rsv1 locus and it exhibits a unique reaction to the SMV strain groups, assignment of a new gene symbol, Rsv1-r, to replace Rsv2 would seem appropriate. Further research is ongoing to investigate the possible existence of the Rsv2 locus in OX670 and its relatives.