The core meiotic transcriptome in budding yeasts.

We used high-density oligonucleotide microarrays to analyse the genomes and meiotic expression patterns of two yeast strains, SK1 and W303, that display distinct kinetics and efficiencies of sporulation. Hybridization of genomic DNA to arrays revealed numerous gene deletions and polymorphisms in both backgrounds. The expression analysis yielded approximately 1,600 meiotically regulated genes in each strain, with a core set of approximately 60% displaying similar patterns in both strains. Most of these (95%) are MATa/MATalpha-dependent and are not similarly expressed in near-isogenic meiosis-deficient controls. The transcript profiles correlate with the distribution of defined meiotic promoter elements and with the time of known gene function.

Direct allelic variation scanning of the yeast genome.

As more genomes are sequenced, the identification and characterization of the causes of heritable variation within a species will be increasingly important. It is demonstrated that allelic variation in any two isolates of a species can be scanned, mapped, and scored directly and efficiently without allele-specific polymerase chain reaction, without creating new strains or constructs, and without knowing the specific nature of the variation. A total of 3714 biallelic markers, spaced about every 3.5 kilobases, were identified by analyzing the patterns obtained when total genomic DNA from two different strains of yeast was hybridized to high-density oligonucleotide arrays. The markers were then used to simultaneously map a multidrug-resistance locus and four other loci with high resolution (11 to 64 kilobases).

Working memory and retrieval: a resource-dependent inhibition model.

Four experiments examined individual differences in working memory (WM) capacity and how those differences affect performance on retrieval from both primary and secondary memory. The results showed that WM differences appear only in retrieval from primary memory and then only under conditions that lead to interference or response competition within the task. This suggests that WM capacity is important to retrieval that is based on controlled effortful search but not search that is based on automatic activation. A view is presented suggesting that individual differences in attentional resources lead to differences in the ability to inhibit or suppress irrelevant information. The paradigm also allowed more general comparisons between the processes involved in retrieval from primary and secondary memory. As expected, it was found that retrieval from primary memory was a function of set size. However, for sets larger than 2 items, retrieval from secondary memory was independent of set size.

A controlled-attention view of working-memory capacity.

In 2 experiments the authors examined whether individual differences in working-memory (WM) capacity are related to attentional control. Experiment 1 tested high- and low-WM-span (high-span and low-span) participants in a prosaccade task, in which a visual cue appeared in the same location as a subsequent to-be-identified target letter, and in an antisaccade task, in which a target appeared opposite the cued location. Span groups identified targets equally well in the prosaccade task, reflecting equivalence in automatic orienting. However, low-span participants were slower and less accurate than high-span participants in the antisaccade task, reflecting differences in attentional control. Experiment 2 measured eye movements across a long antisaccade session. Low-span participants made slower and more erroneous saccades than did high-span participants. In both experiments, low-span participants performed poorly when task switching from antisaccade to prosaccade blocks. The findings support a controlled-attention view of WM capacity.

The nasopharyngeal bacterial flora in the sudden infant death syndrome.

The nasopharyngeal bacterial flora in babies who had died of the sudden infant death syndrome (SIDS) (n = 46) and in healthy infants aged 2 weeks to 6 months (n = 46) is described. Of those who had died, 41.3% carried Staphylococcus aureus (95% confidence limits: 27.3-55.3%) compared with 28.3% of healthy infants (95% confidence limits: 15.3-41.3%). The isolation rate of streptococci was 78.3% in cases (95% confidence limits: 66.4-90.2%) and 32.6% in healthy infants (95% confidence limits: 19.1-46.1%) (significant difference P less than 0.0001). Enterobacteria were isolated from 45.6% of cases (95% confidence limits: 31.2-60%) but only 2.2% of healthy infants (95% confidence limits 0-6.4%) (significant difference, P less than 0.0001). These results indicate a disordered nasopharyngeal flora in SIDS. They also provide baseline data for investigating the hypothesis that common bacterial toxins are involved in the pathogenesis of SIDS.

The cocktail party phenomenon revisited: the importance of working memory capacity.

Wood and Cowan (1995) replicated and extended Moray's (1959) investigation of the cocktail party phenomenon, which refers to a situation in which one can attend to only part of a noisy environment, yet highly pertinent stimuli such as one's own name can suddenly capture attention. Both of these previous investigations have shown that approximately 33% of subjects report hearing their own name in an unattended, irrelevant message. Here we show that subjects who detect their name in the irrelevant message have relatively low working-memory capacities, suggesting that they have difficulty blocking out, or inhibiting, distracting information.

The time-course of negative priming: little evidence for episodic trace retrieval.

An episodic trace retrieval (ETR) explanation of negative priming (NP) predicts that the NP effect should be sensitive to the timing of delays between trials (Neill & Valdes, 1992; Neill, Valdes, Terry, & Gorfein, 1992). Specifically, according to ETR, (1) NP is affected by the response-stimulus interval (RSI) before the prime display, and (2) NP decays when RSI is manipulated within groups but not when RSI is manipulated between groups. Two localization tasks and two identification tasks are reported that question the reliability of these findings. The results suggest that there is little in the time-course literature that uniquely supports the ETR theory of NP. Instead, the results seem more compatible with either a dual-mechanism account (Kane, May, Hasher, Rahhal, & Stoltzfus, 1997) or an integrative approach that incorporates both memory and attention processes (Milliken, Joordens, Merikle, & Seiffert, 1998).

Individual differences in working memory capacity: more evidence for a general capacity theory.

The causes of the positive relationship between comprehension and measures of working memory capacity remain unclear. This study tests three hypotheses for the relationship by equating the difficulty, for 48 individual subjects, of processing demands in complex working memory tasks. Even with difficulty of processing equated, the relationship between number of words recalled in the working memory measure and comprehension remained high and significant. The results favour a general capacity view. We suggest that high working memory span subjects have more limited-capacity attentional resources available to them than low span subjects and that individual differences in working memory capacity will have implications for any task that requires controlled effortful processing.

The effect of memory load on negative priming: an individual differences investigation.

The effect of a verbal (Experiment 1) and a nonverbal (Experiment 2) memory load on negative priming was investigated by employing a concurrent memory task with a letter naming task. Across both experiments, negative priming was reliable only under conditions of zero memory load, suggesting that the processes that contribute to negative priming are resource demanding and dependent on a domain-free resource pool. Individual differences in negative priming were observed, such that high working memory capacity subjects showed reliable negative priming whereas low working memory capacity subjects did not. The results suggest that the negative priming effect results from allocation of controlled attention and that individual differences in working memory capacity correspond to the ability to efficiently handle irrelevant information.

Sequence and analysis of chromosome 1 of the plant Arabidopsis thaliana.

The genome of the flowering plant Arabidopsis thaliana has five chromosomes. Here we report the sequence of the largest, chromosome 1, in two contigs of around 14.2 and 14.6 megabases. The contigs extend from the telomeres to the centromeric borders, regions rich in transposons, retrotransposons and repetitive elements such as the 180-base-pair repeat. The chromosome represents 25% of the genome and contains about 6,850 open reading frames, 236 transfer RNAs (tRNAs) and 12 small nuclear RNAs. There are two clusters of tRNA genes at different places on the chromosome. One consists of 27 tRNA(Pro) genes and the other contains 27 tandem repeats of tRNA(Tyr)-tRNA(Tyr)-tRNA(Ser) genes. Chromosome 1 contains about 300 gene families with clustered duplications. There are also many repeat elements, representing 8% of the sequence.