Browsing by Subject "Male Fertility"
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Item Bringing men in: an analysis of male and female fertility(2009-05-15) Zhang, Li 1976-Prior research has focused on studying female fertility, but male fertility remains overlooked. Using data from the 2001 Demographic Yearbook, the 1964 to 2002 Taiwan-Fukien Demographic Yearbooks, the 2004 National Statistics Reports and the 2002 National Survey of Family Growth (NSFG) Cycle 6, this dissertation examines male and female fertility at the aggregate and individual levels by studying men?s and women?s fertility differentials in rates and in determinants. Based on examining the age-specific fertility rates (ASFRs) and the total fertility rates (TFRs) for men and women during the 1990 to 1998 period in 43 countries and places, results show that male and female age-specific fertility mainly differs in the older age groups. In those age groups, male fertility largely outnumbers female fertility. And this pattern is especially apparent in low fertility countries (TFR<2,200). With regard to total fertility, male and female TFRs tend to be similar in countries with TFR values lower than 2,200 where female fertility tends to be higher than male fertility. The opposite pattern is true for countries with male and female TFRs higher than 2,200. In the analysis of Taiwan fertility, results reveal that male and female TFRs for most years during 1975 to 2004 are far from identical. The ASFRs for men and women also differed over time and varied by educational attainment. Although fertility determinants at the aggregate level impact men?s and women?s fertility similarly, models combining these factors are more powerful when explaining female than male fertility. The individual level analyses of the U.S. samples also show significant fertility differentials by gender. Age, marriage, and Hispanic origin increase men?s fertility to a greater extent compared to women?s fertility. Family income increases men?s fertility but decreases women?s fertility. Participating in the labor force shows a much stronger positive effect on male than on female childbearing. Cohabitation experience, however, has a significantly stronger impact increasing women?s than men?s fertility. And an increased number of sexual partners is more likely to reduce men?s children compared to women. These findings reported draw research attention to male fertility and contribute to understanding the dynamics of male fertility.Item Structure and function of the deleted in azoospermia gene(2009-05-15) Sprague, David Chase CameronA number of genes have been associated with variation in human spermatogenesis related to fertility. One of these, the Deleted in Azoospermia (DAZ) gene, exists as copies on two chromosomes, 3 and Y. The autosomal copy, DAZ-like (DAZL), has one RNA recognition motif (RRM) and is homologous to the DAZL gene found throughout the vertebrate lineage. There are four copies of DAZ on the Y chromosome with a pair at each of two sites. One pair contains a single RRM and the other has three RRMs. Human DAZ is homologous to genes in old world primates and ape Y chromosomes. Both DAZ and DAZL bind messenger RNAs at U-rich sequences near the poly-A tail in a manner that facilitates translation. Both are expressed in spermatogonia during the transition from mitotic cellular expansion through meiotic chromosomal reduction and during spermiogenesis. This study examined genomic variation in DAZ and DAZL, including deletion of DAZ from individuals with various levels of sperm cell production and mutations of DAZL in male partners of infertile couples. Deletions in DAZ are not as common in azoospermic men from central Texas as compared to other reports. Single nucleotide polymorphisms (SNPs) were identified in anonymous infertility patients, but were not located in the exons of the RRM. Proteins produced from transcripts encoded by genes from human DAZL, DAZL with SNPs within and outside the RRM, and a DAZ with single RRM were identified. Binding activity of DAZL to mRNA was confirmed using a microarray method, and mRNA from human testes was screened to identify at least 1,313 mRNA potential targets for DAZL. These targets were involved in ribosome construction, pyruvate metabolism, cell cycle control, and proteasome function. Variations in binding of protein to a high and a low bound target mRNA were demonstrated between protein constructs of DAZL, DAZL with mutations, and DAZ. Binding of DAZL to mRNA was also confirmed using electrophoretic mobility shift assays. With materials and procedures developed during this study, comparisons of genetic variants of DAZ and DAZL can be performed to identify mechanisms responsible for structural and functional differences in control of spermatogenesis.