Pre-Service Primary School Teachers’ Perceptions of Their Understanding of an Enquiry Based Approach to Teaching Primary School Science and Its Influence on Their Field Teaching Experiences

This study seeks to explore pre-service primary school teachers’ perceptions of their understanding of an enquiry based approach to teaching primary school Science. The study also seeks to identify how pre-service primary school teachers perceive the effectiveness of their University Science courses in preparing them to teach science using an enquiry approach. Participants were pre-service teachers enrolled in the B.Ed programme at The University of Trinidad and Tobago. Data were collected using semi-structured interviews. The data revealed that the teachers understood the concept of guided enquiry and knew how to develop lesson plans that incorporate that approach. Although the teachers believed that their courses prepared them adequately to teach primary school Science using enquiry, they encountered problems because of the lack of adequate resources

Effect of Ionic Liquid Electrolytes in DSSCs with Titanium Dioxide (TiO2) Inverse Opal Structures

Dye-sensitized solar cells (DSSC) are low-cost alternatives to conventional solar cells that can work well in low-light conditions. Despite considerable study on improving the efficiency of DSSCs, the current liquid electrolyte cell has plateaued at a conversion efficiency of ~ 12%. A major problem with these cells regarding their applicability is the low viscosity and high volatility of the toxic electrolyte, i.e., acetonitrile, which cause leakage and volatilization. We propose that using ionic liquids (ILs), which are more viscous, less volatile, and conductive, may be more suitable electrolytes. However, one unwanted side effect of the higher viscosity of the ILs may be an incomplete infiltration of the DSSC’s nanoporous TiO2 electrode. Here, we present a study of DSSCs with TiO2 inverse opal electrodes of controlled pore sizes (0.1-1 m) and ionic liquid derivatives of 1-alkyl-3-methylimidazolium tetrafluoroborate (alkyl: ethyl, butyl, and decyl) with viscosities ranging from 25.2 to 721 cP. The stability and functionality of the DSSCs is tested using electrochemical techniques that yield current-voltage and power curves

Developmental genetic studies on Thiobacillus ferrooxidans

Thiobacillus ferrooxidans is an industrially important bacterium which is used in bioleaching operations. The work reported in this investigation extends current knowledge of the genetics of this organism. Conjugation was attempted as a means for plasmid DNA transfer to T. ferrooxidans. Recombinant T. ferrooxidans plasmids, pDER401 and pDER405, were shown to code for mobilization and replication functions in Escherichia coli and Thiobacillus novellus strains. The plasmids were mobilizable at high frequency by the IncP plasmid, R68.45. Attempts to transfer the T. ferrooxidans recombinant plasmids directly from E. coli to T. ferrooxidans were unsuccessful. In multistage mating experiments, plasmid DNA was transferred from E. coli to T. novellus, and from T. novellus to Thiobacillus intermedius. However, in subsequent matings, plasmid transfer from these thiobacilli to T. ferrooxidans could not be shown. A genomic library of T. ferrooxidans ATCC 33020 was constructed in the plasmid vector, pEcoR251, for the purpose of cloning a recA-like gene from this organism. The library consisted of approximately 1,78 X 10⁴ clones carrying chromosomal DNA fragments of about 3-12 kilobases (kb). The library was successfully screened for functional complementation of E. coli auxotrophic mutants. Clones that conferred resistance to methyl methane sulfonate (MMS), a DNA-damaging agent, were isolated in an E. coli recA⁻ mutant. In an attempt to clone a homologous marker, T. ferrooxidans ATCC 33020 was mutated to rifampicin resistance (Rifʳ) and DNA from the mutant strain was used in the construction of plasmid- and cosmid-based libraries. The plasmid library contained approximately 1,35 X 10⁴ clones with inserts of about 1-13 kb. The cosmid library consisted of approximately 8.2 X 10³ colonies, 4.0 X 10⁴ in vitro packaged cosmids, and an amplified in vivo-packaged cosmid lysate containing approximately 1.82 X 10¹¹ infectious particles, carrying inserts of about 35-55 kb. Complementation of E. coli auxotrophic mutants was observed with the plasmid and cosmid library of the T. ferrooxidans Rifʳ strain. Screening both libraries for a Rifʳ marker was unsuccessful. Three recombinant plasmids, pRSR100, pRSR101, and pRSR102, each containing the functional analogue of the E. coli recA gene, were isolated from the plasmid-based genomic library of T. ferrooxidans ATCC 33020. The plasmid, pRSR100, was used for further characterization of the cloned recA-like gene. pRSR100 complemented defects in DNA repair and homologous recombination in an E. coli recA- strain. Antiserum raised against E. coli RecA⁻ protein reacted with two protein bands with an apparent Mᵣ of approximately 40 000 and 38 000 in extracts of the recA deletion mutant, E. coli JK696, containing pRSR100. A single band with an apparent Mᵣ of approximately 40 000 was detected in T. ferrooxidans cell extracts with the E. coli RecA antiserum. The nucleotide sequence of the T. ferrooxidans recA gene has been determined. No SOS box characteristic of LexA- regulated promoters could be identified in the 196-bp region upstream of the coding region. The T. ferrooxidans recA gene specifies a protein of 346 amino acids that has 66% and 69% homology to the RecA proteins of E. coli and P. aeruginosa, respectively. Most amino acids that have been identified as being of functional importance in the E. coli RecA protein are conserved in the T. ferrooxidans RecA protein. Although some amino acids that have been associated with ATPase and constitutive protease activity have been substituted, the cloned protein has retained these activities. The cloned recA gene was expressed in E. coli from both the λ Pᵣ and lac promoters. However, no expression from the 2.2 kb T. ferrooxidans DNA preceding the gene was evident

<i>P. berghei</i> telomerase subunit TERT is essential for parasite survival

Telomeres define the ends of chromosomes protecting eukaryotic cells from chromosome instability and eventual cell death. The complex regulation of telomeres involves various proteins including telomerase, which is a specialized ribonucleoprotein responsible for telomere maintenance. Telomeres of chromosomes of malaria parasites are kept at a constant length during blood stage proliferation. The 7-bp telomere repeat sequence is universal across different Plasmodium species (GGGTTT/CA), though the average telomere length varies. The catalytic subunit of telomerase, telomerase reverse transcriptase (TERT), is present in all sequenced Plasmodium species and is approximately three times larger than other eukaryotic TERTs. The Plasmodium RNA component of TERT has recently been identified in silico. A strategy to delete the gene encoding TERT via double cross-over (DXO) homologous recombination was undertaken to study the telomerase function in P. berghei. Expression of both TERT and the RNA component (TR) in P. berghei blood stages was analysed by Western blotting and Northern analysis. Average telomere length was measured in several Plasmodium species using Telomere Restriction Fragment (TRF) analysis. TERT and TR were detected in blood stages and an average telomere length of ~950 bp established. Deletion of the tert gene was performed using standard transfection methodologies and we show the presence of tert− mutants in the transfected parasite populations. Cloning of tert- mutants has been attempted multiple times without success. Thorough analysis of the transfected parasite populations and the parasite obtained from extensive parasite cloning from these populations provide evidence for a so called delayed death phenotype as observed in different organisms lacking TERT. The findings indicate that TERT is essential for P. berghei cell survival. The study extends our current knowledge on telomere biology in malaria parasites and validates further investigations to identify telomerase inhibitors to induce parasite cell death

Genetic mapping of retinitis pigmentosa implications for South African patients

No Abstract

Digitotalar dysmorphism: Molecular elucidation

Dominantly inherited digitotalar dysmorphism (DTD), which is characterised by flexion contractures of digits and ‘rocker-bottom’ feet due to a vertical talus, was first described in a South African family of European stock in 1972. We review the clinical manifestations and document the molecular basis for DTD in this prototype family. This family was restudied in 1995 and 2006 and biological specimens were obtained for molecular studies. Since the distal arthrogryposes (DAs) are genetically heterogeneous, an unbiased approach to mutation identification was undertaken through whole-exome next-generation sequencing of DNA from a single DTD-affected female. Venous blood specimens were obtained for DNA banking and subsequent molecular studies. Analysis of the nine genes that had previously been shown to cause DAs revealed a pathogenic mutation in exon nine of TNNT3. The presence of the p.(Arg63His) missense mutation at position 63 of TNNT3 was confirmed through direct cycle sequencing of genomic DNA in six affected family members for whom DNA had been archived

Copper(I), Palladium(II) and Platinum(II) complexes of the 2- diphenylphosphino-1,10-phenanthroline ligand.

Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998Chapter 1 reviews the coordination behaviour of the 6-diphenylphosphino-2,2'-bipyridine, 6-anilino-2,2'-bipyridine, 2,2'-bipyridyl-6-one, 6-N-methylanilino-2,2'-bipyridine, 6-piperidyl-2,2'-bipyridine and 2-(phenylamino)-1,10-phenanthroline ligands. These ligands are all tridentate and contain well established chelating fragments viz., 2,2'-bipyridine and 1,10-phenanthroline. Thus the review of their coordination provides insight into the expected coordination of the 2-diphenylphosphino-1,10-phenanthroline (Ph2Pphen) ligand. The synthesis and characterisation of this ligand is described in Chapter 2. Chapter 3 describes the synthesis and characterisation of a range of Ph2Pphen ligand-bridged dicopper(l) complexes. It has been shown that Ph2Pphen reacts with a suitable copper(l) precursor, [Cu(MeCN)4]+, to form the versatile dinuclear [Cu2(u-Ph2Pphen)2(MeCN)2]2+complex cation containing two bridging Ph2Pphen ligands; the structure of the SbF6 salt of this complex has been determined X-ray crystallographically. This complex possesses labile acetonitrile ligands which have been substituted by a variety of neutral and anionic ligands. Complexes prepared this way include [Cu2(u-Ph2Pphen)2(u-CI)]+, [Cu2(u-Ph2Pphen)2(u-I)]+, [Cu2(u-Ph2Pphen)2(py)2]2 +, [Cu2(u-Ph2Pphen)2{u-S2CN(Et)2}]+, [Cu2(u-Ph2Pphen)2(n-bipy)]2+ and [Cu2(u-Ph2Pphen)2(n-phen)]2+. X-ray structure determinations have been completed for [Cu2(u-Ph2Pphen)2{u-S2CN(Et)2}]+ and [Cu2(u-Ph2Pphen)2(n-bipy)]2+. The X-ray crystal structures of these ligand-bridged complexes confirm that the phosphorus atom coordinates to one copper atom while the phenanthroline fragment chelates to the other copper atom with the result that each metal atom has a tetrahedral geometry. Chapter 4 reviews the synthesis and characterisation of palladium and platinum complexes of the 2-diphenylphosphino-1, 10-phenanthroline (Ph2Pphen) ligand. The comproportionation reaction with Pd(II) and Pd(0) afforded the dinuclear complex [Pd2(u-Ph2Pphen)2](BF4)2. The reaction of Ph2Pphen with platinum resulted in ill-defined products that could not be isolated and characterised

Salivary gland-specific <i>P. berghei</i> reporter lines enable rapid evaluation of tissue-specific sporozoite loads in mosquitoes

Malaria is a life-threatening human infectious disease transmitted by mosquitoes. Levels of the salivary gland sporozoites (sgs), the only mosquito stage infectious to a mammalian host, represent an important cumulative index of &lt;i&gt;Plasmodium&lt;/i&gt; development within a mosquito. However, current techniques of sgs quantification are laborious and imprecise. Here, transgenic &lt;i&gt;P. berghei&lt;/i&gt; reporter lines that produce the green fluorescent protein fused to luciferase (GFP-LUC) specifically in sgs were generated, verified and characterised. Fluorescence microscopy confirmed the sgs stage specificity of expression of the reporter gene. The luciferase activity of the reporter lines was then exploited to establish a simple and fast biochemical assay to evaluate sgs loads in whole mosquitoes. Using this assay we successfully identified differences in sgs loads in mosquitoes silenced for genes that display opposing effects on &lt;i&gt;P. berghei&lt;/i&gt; ookinete/oocyst development. It offers a new powerful tool to study infectivity of &lt;i&gt;P. berghei&lt;/i&gt; to the mosquito, including analysis of vector-parasite interactions and evaluation of transmission-blocking vaccines

A Founder Mutation in MYO7A Underlies a Significant Proportion of Usher Syndrome in Indigenous South Africans: Implications for the African Diaspora

PURPOSE. Research over the past 25 years at the University of Cape Town has led to the identification of causative mutations in 17% of the 1416 families in the Retinal Degenerative Diseases (RDD) biorepository in South Africa. A low rate of mutation detection has been observed in patients of indigenous African origin, hinting at novel genes and mutations in this population. Recently, however, data from our translational research program showed two unrelated indigenous African families with Usher syndrome (USH), with the same homozygous MYO7A mutation. Therefore, the extent to which this mutation contributes toward the disease burden in South Africa was investigated. METHODS. Cohorts of unrelated indigenous South African probands with different RDD diagnoses were tested for the MYO7A c.6377delC mutation. Familial cosegregation analysis was performed for homozygous probands, clinical data were evaluated, and SNP haplotypes were analyzed. RESULTS. This homozygous MYO7A mutation underlies a remarkable 43% of indigenous African USH cases investigated in this study, the majority of which (60%) were diagnosed clinically with Type 2 USH. All homozygotes shared a common haplotype. This mutation does not appear to cause nonsyndromic vision loss. CONCLUSIONS. Of interest is the origin of this common mutation relevant to the Bantu population migration into southern Africa. Further investigation of the phenotype may elucidate the disease biology, and perhaps reveal a larger cohort with the same mutation, with which to assess the impact of environmental and genetic modifiers and evaluate therapeutic trials