Magister Scientiae - MSc (Biochemistry)
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Browsing by Author "Hendricks, Denver"
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Item The adenomatous polyposis coli (APC) and p53 gene status in South African oesophageal cancer patients(University of the Western Cape, 1996) Skelton, Michelle; Hendricks, Denver; Smith, ArleneOesophageal cancer is the most conmon cause of cancer-related deaths in black males in South Africa. In an effort to understand the molecular nature of oesophageal carcinogenesis in South Africa, two tumour suppressor genes, Adenomatous Polyposis Coli (APC) and p53, were examined in normal and tumour tissue obtained from 33 oesophageal cancer patients. Several studies have shown that alterations of the APC and p53 genes are associated with the development of cancer. Allelic loss at the APC gene locus was examined using two polymorphic markers within the coding region of the APC gene. Single stranded conformation polymorphism, heteroduplex and DNA sequencing analyses were used to detect mutations in the mutation susceptible regions of the APC and p53 genes. The "Mutation Cluster Region" (MCR) in exon 15 of the APC gene was examined. Only exons 5 and 6 in the "hot spot" region of the p53 gene were examined. An allelic loss of 21% (4 of 19 informative cases) and an informativity of 59Yo (19 of 32) of the APC gene was demonstrated in patients analysed. No somatic mutations were detected in the MCR in exon 15 of the APC gene. Three putative mutations were detected in the p53 gene using SSCP and HD analysis, two of which were confirmed by DNA sequencing. Analysis of one patient revealed a TCA to TGA base substitution at codon 183 in exon 5 of the p53 gene, resulting in a stop codon at that position. An eleven base pair deletion in exon 6 of the p5 3 gene was detected in another patient. This deletion caused a frame shift mutation and culminated in a premature stop codon 13 codons downstream. Overall, a mutation frequency of 8% (2 of 25 patients analysed) was detected for the p53 gene with exons 7 and 8 still pending further study. These results suggest that the APC gene may not be involved in oesophageal cancer in South Africa and further studies are necessary in order to examine the role of thep53 gene in this disease in South Africa.Item Genetic variation between two subspecies of Reedfrogs in the genus Hyperolius (Anura: Hyperoliidae)(University of the Western Cape, 1993) Hess, Anthony Jacobus; Hendricks, DenverThe frog genus Hyperolius is the largest of 19 genera in the Hyperoliidae (Channing, 1939). The members of the genus display considerable morphological homogeneity with a diversity of dorsal colour patterns. The genus is endemic to Africa and is distributed throughout the wetlands south of the Sahara excluding the western plateau slopes and South African plateau. They are found in close proximity to water, on reeds, sedges and also on water-lily leaves (Iambiris, 1989). The South African forms are commonly referred to as reedfrogs (Passmore and Camrthers, 1979). The members of the genus bury themselves in the ground and under leaves during the dry season and emerge after the first rains (Iambiris, 1989). The eggs are laid in water, attached to waterplants, but certain species deposit eggs above the water level or between water-lily leaves (Lambiris, 1989). Characters that disqinguish the genus from other African genera are as follows: The pupil is horizontal to round; Vomerine teeth are absent; The fingers and toes are webbed; The oral disc is ventrally situated (Passmore and Camrthers, 1979).Item "Genetic variation between two subspecies of reedfrogs in the genus Hyperolius (Anura: Hyperoliidae)"(University of the Western Cape, 1993) Hess, Anthony Jacobus; Hendricks, DenverH. m. broadleyi and H. m. verrucosus are not only different in terms of colour pattern, but distinct genetic differences were detected in restriction site maps of their ribosomal DNA. A sequence divergence value of 13,8% was found between the subspecies. This value exceeds the range recorded between separate species of the genus Rana, ie. 2,2 % between Rana pustulosa and Rana tarahumarae, and 10, 1 % between Rana pustulosa and Rana pipiens. The value of 13,8% between the subspecies is also in the same range as that found between was detected between samples from three different localities within the distribution range of H. m. verrucosus. The genetic data associated with the different colour patterns, suggests that H. m. broadleyi and H. m. verrucosus can be regarded as distinct species. However, a similar study should be performed to examine the genetic status of the subspecies forming the gradient along the east coast of southern Africa. Although the effect of concerted evolution (as discussed in Chapter 2) allows for small sample sizes it would be useful to examine a large number of individuals especially from the overlap zones to determine the extent of genetic heterozygosity and to determine if similar genetic differences (found between H. m. broadleyi and H. m. verrucosus) exist between the rest of the subspecies. The current study has shown that genetic evaluation of all the southern African H. marmoratus subspecies could have a positive impact on the taxonomy of this group of frogs which is still unresolved. This study has identified at least two species within the H. marmoratus complex and it is possible that more species exist within the group. Because of morphological homogeneity it will be difficult to use morphological characters, but more than one molecular technique can be utilized to verify results obtained with one technique.