A model and lexicon for pollen fate

As pollination biology undergoes unprecedented growth as a discipline, confusion in the use of terms has become increasingly common. The need for a flexible yet unambiguous terminology has become urgent. As an example we discuss how the term “pollination efficiency” is used differently by 18 studies, and “pollinator effectiveness” by seven others. Here we present flowcharts of two general models of pollination systems (biotic and abiotic) that trace all the events from pollen production to development of seed or fruit, and we develop a lexicon for the quantities of pollen, processes of transfers (to a vector, to a stigma), and ratios of quantities that are of interest in studies of pollination and mating systems. An appendix includes a glossary of the definitions we suggest.     

Chromosome painting of Amigo wheat

Chromosome painting using multicolor fluorescence in situ hybridization showed that, in addition to the T1AL·1RS translocation derived from rye, a segment from chromosome 3Ae#1 of Agropyron elongatum (2n=10x =70), is present in Amigo wheat. The Agropyron chromosome segment is located on the satellite of chromosome 1B and the translocation chromosome is designated as T1BL·1BS-3Ae#1L. T1BL·1BS-3Ae#1L was inherited from Teewon wheat and carries resistance genes to stem rust (Sr24) and leaf rust (Lr24). The Agropyron chromosome segments in different Sr24/Lr24 carrier wheat lines, including Agent, TAP 48, TAP 67, Teewon, and Amigo, showed a diagnostic C-band, and were derived from the same chromosome, 3Ae#1.     

Transfer of Ph I genes promoting homoeologous pairing from Triticum speltoides to common wheat

Diploid-like chromosome pairing in polyploid wheat is controlled by several Ph (pairing homoeologous) genes with major and minor effects. Homoeologous pairing occurs in either the absence of these genes or their inhibition by genes from other species (Ph ^I genes). We transferred Ph ^I genes from Triticum speltoides (syn Aegilops speltoides) to T. aestivum, and on the basis of further analysis it appears that two duplicate and independent Ph ^I genes were transferred. Since Ph ^I genes are epistatic to the Ph genes of wheat, homoeologous pairing between the wheat and alien chromosomes occurs in the F₁ hybrids. Using the Ph ^I gene stock, we could demonstrate homoeologous pairing between the wheat and Haynaldia villosa chromosomes. Since homoeologous pairing occurs in F₁ hybrids and no cytogenetic manipulation is needed, the Ph ^I gene stock may be a versatile tool for effecting rapid and efficient alien genetic transfers to wheat.Contribution no. 93-435-J from the Kansas Agricultural Experiment Station, Kansas State University, Manhattan, KS 66506-5502, USA     

Genetic mapping of 14 short tandem repeat polymorphisms on human chromosome 22

We have constructed a linkage map of 14 short tandem repeat polymorphisms (11 with heterozygosity > 70%) on the long arm of human chromosome 22 using 23 non-CEPH pedigrees. Twelve of the markers could be positioned uniquely with a likelihood of at least 1,000:1, and distributed at an average distance of 6.62 cM (range 1.5–16.1 cM). The sex-combined map covers a total of 79.6 cM, the female map 93.2 cM and the male map 64.6 cM. Based on comparisons between physical maps and other genetic maps, we estimate that our map covers 70%–80% of the chromosome. The map integrates markers from previous genetic maps and uniquely positions one marker (D22S307). Data from physical mapping on the location of four genetic markers correlates well with our linkage map, and provides information on an additional marker (D22S315). This map will facilitate high resolution mapping of additional polymorphic loci and disease genes on chromosome 22, and act as a reference for building and verifying physical maps.     

Tandem-repeat internal mapping (TRIM) of the involucrin gene: repeat number and repeat-pattern polymorphism within a coding region in human populations.

We have analyzed the human involucrin gene in 41 British African-Caribbeans and 37 British white Caucasians by tandem-repeat internal mapping and DNA sequencing. A point mutation (i.e., Bc) in the last B repeat unit was found in 98.6% of British white Caucasians and in 52.4% of British African-Caribbeans. The distribution of repeat patterns was also different between the two populations. Nine previously unreported repeat pattern alleles, 4 with and 5 without the Bc repeat, have been found, increasing the range of variation in humans to 15 reported repeat patterns, 6 with and 9 without the Caucasian mutation. Three further sequence variations, each occurring in a single individual, were found. The evolutionary significance of variation in the human involucrin gene is discussed.     

A study of the association between schizophrenia and the dopamine D3 receptor gene

A study of the genetic association between schizophrenia and aBalI polymorphism in exon 1 of the dopamine D₃ (DRD3) gene, a candidate gene for schizophrenia, was conducted. The polymorphism was examined in 91 patients whose symptoms satisfied DSM-III-R for schizophrenia and 90 controls. There were no significant differences between the groups in allele frequencies or genotype counts. Contrary to a previous report, the patients were no more likely to be homozygous than controls. Moreover, no association with the presence of illness could be demonstrated when the patients were grouped according to sex, age of onset, history of admission to psychiatric institutions or positive family history.     

Conservation of motifs within the unusually variable polypeptide sequences of type I restriction and modification enzymes

Type I restriction enzymes comprise three subunits encoded by genes designated hsdR, hsdM, and hsdS; S confers sequence specificity. Three families of enzymes are known and within families, but not between, hsdM and hsdR are conserved. Consequently, interfamily comparisons of M and R sequences focus on regions of putative functional significance, while both inter- and intrafamily comparisons address the origin, nature and role of diversity of type I restriction systems. We have determined the sequence of the hsdR gene for EcoA, thus making available sequences of all three hsd genes of one representative from each family. The predicted R polypeptide sequences share conserved regions with one superfamily of putative helicases, so-called ‘DEAD box’ proteins; these conserved sequences may be associated with the ATP-dependent translocation of DNA that precedes restriction. We also present hsdM and hsdR sequences for EcoE, a member of the same family as EcoA. The sequences of the M and R genes of EcoA and EcoE are at least as divergent as typical genes from Escherichia coli and Salmonella, perhaps as the result of selection favouring diversity of restriction specificities combined with lateral transfer among different species.     

Clinical and epidemiologic characteristics of hepatitis C in a gastroenterology/hepatology practice in Ottawa.

OBJECTIVE: To examine the clinical and epidemiologic features of hepatitis C virus (HCV) infection in a gastroenterology/hepatology practice in Ottawa. DESIGN: Retrospective chart review. PATIENTS: Sixty-three consecutive patients found to be anti-HCV positive. Their charts were analysed with respect to risk factors, history of hepatitis, serum aspartate aminotransferase (AST) levels and the presence of hepatitis B markers. The long-term sexual partners of 29 patients agreed to undergo HCV antibody testing. RESULTS: Of the patients 48 (76%) had been exposed to HCV parenterally: 27 used intravenous drugs, and 21 had received blood or blood products. Eleven patients did not have any known risk factor (sporadic infection), but eight of them had lived in countries where hepatitis C may be more prevalent; the other three had locally acquired infection. The mean serum AST level at the first visit was 140 (normally less than 40) IU/L. At least one hepatitis B marker was identified in 33% of the patients. None of the sexual partners who were tested were anti-HCV positive. CONCLUSION: Most cases of hepatitis C in Ottawa are acquired through parenteral exposure; sexual transmission is rare. Sporadic infection in the Ottawa region is rare but may be more common in people from countries with a higher prevalence rate of hepatitis C. Most cases of hepatitis C are asymptomatic.