The effects of date of planting on field establishment of serotinous cape Proteaceae

Season of fire have marked effects on the germination and establishment of serotinous shrubs of the family Proteaceae in fynbos vegetation. To investigate reasons for this, we simulated the effects of different fire seasons by planting seeds into cleared fynbos and then followed their progress. Four species of Proteaceae were planted monthly at four sites over two and a half years. Exclosures were used to exclude rodent seed predators. Germination was confined largely to the three winter months (June–Aug.). Seeds planted from January–June had higher germination than those planted in the second half of the year. Higher levels of regeneration noted after fires in the first half of the year, were previously hypothesised to be results of predation. However, we obtained similar results despite the exclusion of seed predators. Monthly minimum temperature was strongly correlated with germination percentage but monthly rainfall was not. Loss of seed viability may be important, in determining post-fire seedling densities. Differential seedling mortality of earlier and late germinants appears to be unimportant in determining establishment levels. Our results nevertheless support the current practice of restricting management fires in fynbos to the summer-autumn period.     

The Influence of Texting Language on Grammar and Executive Functions in Primary School Children

When sending text messages on their mobile phone to friends, children often use a special type of register, which is called textese. This register allows the omission of words and the use of textisms: instances of non-standard written language such as 4ever (forever). Previous studies have shown that textese has a positive effect on children’s literacy abilities. In addition, it is possible that children’s grammar system is affected by textese as well, as grammar rules are often transgressed in this register. Therefore, the main aim of this study was to investigate whether the use of textese influences children’s grammar performance, and whether this effect is specific to grammar or language in general. Additionally, studies have not yet investigated the influence of textese on children’s cognitive abilities. Consequently, the secondary aim of this study was to find out whether textese affects children’s executive functions. To investigate this, 55 children between 10 and 13 years old were tested on a receptive vocabulary and grammar performance (sentence repetition) task and various tasks measuring executive functioning. In addition, text messages were elicited and the number of omissions and textisms in children’s messages were calculated. Regression analyses showed that omissions were a significant predictor of children’s grammar performance after various other variables were controlled for: the more words children omitted in their text messages, the better their performance on the grammar task. Although textisms correlated (marginally) significantly with vocabulary, grammar and selective attention scores and omissions marginally significantly with vocabulary scores, no other significant effects were obtained for measures of textese in the regression analyses: neither for the language outcomes, nor for the executive function tasks. Hence, our results show that textese is positively related to children’s grammar performance. On the other hand, use of textese does not affect—positively nor negatively—children’s executive functions.     

De novo t(2;13)(p24.3;q14.2) and retinoblastoma

Summary The two probes H3-8 and H2-42, known to be located in 13q14, were mapped by in situ hybridization to either side of the 13 breakpoint of an apparently balanced de novo t(2;13)(p24.3;q14.2) detected in a patient with retinoblastoma as the only phenotypic manifestation.     

The β heterochromatic sequences flanking the I elements are themselves defective transposable elements

Phylogenetic studies suggest that mobile element families are unstable components of the Drosophila genome. Two examples of immobilization of a transposable element family are presented here: as judged by their constant genomic organization among unrelated strains, the F and I element families have been respectively immobilized for a long time in D. simulans and in the reactive D. melanogaster strains (these are the laboratory strains which escaped the recent I invasion of D. melanogaster natural populations). All the elements of these defective families are located in the heterochromatic portion of the genome. Moreover, most if not all of the heterochromatic sequences into which the defective I elements are embedded are themselves non-mobile members of various nomadic families such as mdg 4, 297, 1731, F and Doc. These results are discussed with special emphasis on the possible nomadic origin of heterochromatin components and on the mechanisms of evolutionary turnover of the transposable element families.