0000000000339641
AUTHOR
P. Vos
Graphing calculator supported instrumentation schemes for the concept of derivative: a case study
This paper reports on the role of the graphing calculator (GC) in the learning of derivatives and instantaneous rate of change. In a longitudinal study, we administered task based interviews before and after the introduction of calculus. We analyzed students’ use of the GC in these interviews. This paper reports on the case of one student, Andy, who is a resilient user of the GC while he develops into a flexible solver of problems on instantaneous rate of change. His case demonstrates that, although the GC is meant to promote the integration of symbolical, graphical and numerical techniques, it can facilitate a learning process in which symbolical techniques develop separately from other te…
Progress in Arabidopsis genome sequencing and functional genomics
Arabidopsis thaliana has a relatively small genome of approximately 130 Mb containing about 10% repetitive DNA. Genome sequencing studies reveal a gene-rich genome, predicted to contain approximately 25 000 genes spaced on average every 4.5 kb. Between 10 to 20% of the predicted genes occur as clusters of related genes, indicating that local sequence duplication and subsequent divergence generates a significant proportion of gene families. In addition to gene families, repetitive sequences comprise individual and small clusters of two to three retroelements and other classes of smaller repeats. The clustering of highly repetitive elements is a striking feature of the A. thaliana genome emer…
Sequence and analysis of chromosome 4 of the plant Arabidopsis thaliana
The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we report one of the first milestones of this project, the sequence of chromosome 4. Analysis of 17.38 megabases of unique sequence, representing about 17% of the genome, reveals 3,744 protein coding genes, 81 transfer RNAs and numerous repeat elements. Heterochromatic regions surrounding the putative centromere, which has not yet been completely sequenced, are characterized by an increased frequency …