Ethnic Considerations for Glaucoma: A Review

Glaucoma is undoubtedly a major worldwide disease and cause of blindness. The term glaucoma however encompasses a group of disorders with differing age of incidence, intraocular pressures and varying degrees of hereditability in which vision loss occurs through a characteristic mode of retinal ganglion cell death. There are also significant differences in frequencies of incidence and gene associations for this group of disorders amongst different groups of populations. The current literature often states definitive trends in incidence for ethnic groups that fail to take into account an overall genetic fine structure for these groups. The present review intends to present an overview of some of the background necessary to discuss the genetic basis of glaucoma before describing some of the literature concerning the illness in Gypsy, Japanese, Scandinavian, Latino (Mexican and Brazilian) and Sub-Saharan African populations. It is intended that this review will give the reader a clearer picture of the diversity of worldwide glaucoma presentation which perhaps prove to question the current Ethnic view.

The early years of molecular biology: personal recollections

The early years of molecular biology were characterized by a strong interaction between theory and experiment. This included the elucidation of the structure of DNA itself; genetic fine structure, recombination and repair; DNA replication; template–directed protein synthesis; the universality of the triplet genetic code, and the co–linearity of the DNA sequence of structural genes and the sequence of amino acids in proteins. The principle of co–linearity was later modified when split genes were discovered.. It is suggested that accurate splicing of gene transcripts might also be template directed. In 1958 Crick proposed a ‘central dogma’ of molecular biology stating that information could not be transmitted from proteins to DNA. Nevertheless, proteins can chemically modify DNA, and this is now known to have strong effects on gene expression.

Analysis of Recombination Sites Within the Maize waxy Locus

Genetic fine structure analysis of the maize wx locus has determined that the ratio of genetic to physical distance within wx was one to two orders of magnitude higher than the average for the maize genome. Similar results have been found at other maize loci. In this study, we examined several mechanisms that could account for this pattern. First, crossovers in two other maize genes resolve preferentially at specific sites. By mapping exchanges between wx-B1 and wx-I relative to a polymorphic SstI site, we found no evidence for such a hotspot at wx. Second, deletion of promoter sequences from wx alleles had little effect on recombination frequencies, in contrast to results in yeast where promoter sequences are important for initiating recombination in some genes. Third, high levels of insertion polymorphism may suppress intergenic recombination. However, the presence of a 2-kb Ds element 470 bp upstream of the wx transcription start site did not further suppress recombination between Ds insertions in nearby wx sequences. Thus, none of these mechanisms is sufficient to explain the difference between intergenic and intragenic recombination rates at wx.