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Studies have discovered higher frequencies of single nucleotide polymorphisms (SNPs) in different mitochondrial genes are associated with subnormozoospermia. However, the frequencies of SNPs in ND1 and ND2 are not unknown. The present research was aimed to determine the frequencies of SNPs in ND1 and ND2 genes of the mitochondrial genome in fertile and subfertile men and whether changes in codon usage was associated with fertility phenotypes. Total genomic DNA from 157 semen samples was extracted using the proteinase K/SDS digestion procedure, followed by phenol/chloroform purification and ethanol precipitation. ND1 and ND2 genes were amplified respectively from 80 and 92 DNA samples from different fertility groups. Each PCR product was sequenced to identify mutations. Codon change resulting from a nucleotide substitution was determined by comparison with a reference mtDNA sequence obtained from the NCBI database. The frequency of codon usage in the reference mtDNA was determined by the computer program MEGA version 2.1. Eleven synonymous nucleotide substitutions and two non-synonymous substitutions were found in this study. Four SNPs were previously characterized; all SNPs were homoplasmic. None of the SNPs were likely to affect the function of the proteins on the basis of the hydrophobicity plots or secondary structure predictions. Sixty two percent of synonymous mutations were found to change from a high to a low relative codon usage values; 37% of synonymous mutations changed from a low to a high relative usage value. Chi-square (χ²) test (χ²= 0.067 with 1 d.f.) showed that there was no significant difference at the 5% level between these changes. Thus, change in codon usage was not related to semen quality in men. Further, there were no statistically significant differences in the observed frequencies of SNPs of fertile and subfertile men. However, the sample size was small and this study was only focused on a single NZ Caucasian population. Further study including larger and more diverse population samples may provide further insight into the functional importance of codon usage and its relevance to fertility

Codeswitching between languages is a uniquely bilingual mode of communication. The purpose of this dissertation is to enhance the current body of knowledge dealing with the phenomenon by analysing samples of speech produced by twenty-six Spanish/English bilingual children ranging in age from eight to twelve. Methods of analysis include theoretical linguistics, sociolinguistics, psycholinguistics, and educational linguistics. A discussion of relevant codeswitching research covering the past thirty years is presented. The data were collected during a reading study focusing on miscue analysis. The children read stories in English and retold them in both Spanish and English. The analysis considers the data from the four previously mentioned points of view. The linguistic analysis looks at the locations of switched constituents within the sentence and the frequency with which those constituents are switched. The data of this study are compared with that of other researchers, and a consideration of a formal grammar of codeswitching is presented. The sociolinguistic analysis addresses the effect of social and stylistic variables on codeswitching. The psycholinguistic analysis of codeswitching covers lexical storage, editing phenomena, and developmental aspects. Finally, some aspects of the education of bilinguals are considered by analysing the effect of the printed word on language switching and dialect shifting . The application of the results of the analysis to both theoretical issues and practical concerns is explored along with suggested areas for future research. The analyses show that young children's codeswitching initially favors less complex structures and is influenced by few social variables. As they grow older, they become more comfortable with switching grammatically complex structures, and they become aware of a greater variety of social factors. A separate grammar is not necessary for a complete description of codeswitching; a modified interdependance model of the two grammars can account for the codeswitching mode. Lastly, the written language becomes part of the speech situation in the classroom and affects the choice of language or dialect spoken.

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