Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 4 uppsatser.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xi, 133 p.; also includes graphics Includes bibliographical references (p. 127-133). Available online via OhioLINK's ETD Center

The centromere is an important region of the chromosome which ensures correct segregation at cell division. The DNA sequences which make up human centromeres are poorly understood. An analysis of the human Y chromosome centromere DNA has therefore been undertaken. The structures of 23 yeast artificial chromosomes (YAC) clones and 4 cosmid clones have been determined and these have contributed to a map of ~7Mb of DNA which span the centromere. The centromeric region of the human Y chromosome contains a single major block of tandemly repeating alphoid DNA which is variable in size. The 5.7kb alphoid subunits are all orientated in one direction and become diverged at the edges of the array. Flanking the alphoid DNA are small blocks of other known tandemly repeated sequences, the 5bp, 48bp and 68bp satellites. These satellites are arranged in an asymmetric manner and are interspersed with a range of low to moderate copy number repeats. Only one putative single copy sequence has been detected. Nearby lie two regions of X-Y homology: a more proximal region which contains a gene (amelogenin) and a more distal region which has previously been shown to result from a recent X-Y transposition event. These results show that the centromeric region of the human Y chromosome is a complex mosaic of tandem repeats and other repeats. Furthermore, they provide a detailed map of the region and thus provide a solid basis for functional studies of candidate centromere determining sequences.

Thesis (Ph.D.)--Kent State University, 2007. / Title from PDF t.p. (viewed Aug. 6, 2008). Advisor: Daniel L Ely. Includes bibliographical references (p. 229-251).

A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Medicine Johannesburg, 2014 / Evolution and historical events over the past 300 000 years have contributed in shaping the gene pool of sub-Saharan African populations. By examining patterns of Y chromosome variation, through the screening of single nucleotide polymorphisms (SNPs) and short tandem repeats (STRs), the present study aimed to characterise the phylogeography of ancient African Y chromosome haplogroups found in populations across sub-Saharan Africa, as well as understand the genetic affinities of these populations. In order to screen the large number of the markers required, seven multiplex single base extension assays were developed. These were used to refine the resolution of Y chromosomes commonly found in Africa, but also included a few markers to delineate the common non-African Y chromosome haplogroups, following a hierarchical screening process. In total, 1667 males were screened, and these data were compiled together with comparative published data. The resultant SNP and STR dataset was used in illustrating, more specifically, the phylogeographies of haplogroups A and B. The wide geographic distribution of haplogroup A, together with its position at the root of the phylogeny and high diversity, support an early diversification of the haplogroup into its subclades, which subsequently spread across Africa. The distribution of major haplogroup B subclades, however, are possibly due to post-glacial migrations in the case of haplogroup B-M112, and recent population expansions, leading to the common presence of haplogroup B-M152 across sub-Saharan Africa. The spread of haplogroup E, however, created the biggest impact on African populations; with its expansion likely resulting in the diminished presence of many of the subclades of haplogroups A and B. The Y chromosome compositions of present sub-Saharan African populations are, thus, the result of several diversification events, followed by migration, and mixing of population groups, over the course of modern human existence.

No description available.

published_or_final_version / Obstetrics and Gynaecology / Master / Master of Philosophy

The long-range structure of the Y chromosome alphoid satellite DNA has been determined in the cell lines 3E7 and OXEN. Variation in alphoid DNA block size and restriction enzyme sites were observed. The alphoid block size and restriction enzyme site variations were determined for a collection of 42 normal Y chromosomes. The alphoid DNA polymorphisms observed denned 24 Y chromosome alleles. Unexpectedly, the Y alphoid DNA alleles analysed revealed two distinct groups of Y chromosomes indicating that most of the Caucasian and Asian men analysed were descended from one of two males. The structure of the alphoid DNA was determined for 25 cell lines expected to contain abnormal Y chromosomes. Six of the cell lines lacked Y chromosomes. Four lacked both alphoid DNA and Y a centromere. 13 out of the remaining 15 Y chromosomes had centromeres and Y alphoid DNA block sizes and restriction enzyme site variation similar to that of normal Y chromosome alphoid DNA. Two of the abnormal cell lines had alphoid DNA blocks significantly different from the normal Y alphoid DNA structure. These results confirm that alphoid DNA is located very close to, or at the centromere and make it a prime candidate for a functional mammalian centromere sequence.

In most societies, surnames are passed down from fathers to sons, just like the Y chromosome. It follows that, theoretically, men sharing the same surnames would also be expected to share related Y chromosomes. Previous investigations have explored such relationships but most data has been collected so far only from the British Isles. In order to provide additional in sights into the con-elation between surnames and Y chromosomes, this study focuses on the Spanish population and investigates Y chromosome SNP/STR variation by analysing a total of 1,766 DNA samples from unrelated Spanish male volunteers belonging to 37 surnames and 355 controls. The results suggest that the degree of coancestry within surnames is highly dependent on surname frequency. Within-surname genetic variation, as measured by different statistics, con-elates well with surname frequency, though a few exceptions are found. In addition, geographic distance between the individuals' place of origin influences Significantly the con-elation between Y chromosome and surnames: men with the same surname tend to have more similar Y chromosomes if their paternal grandfathers were born geographically close to each other. Therefore, it seems that Y chromosome coancestry within surnames is as much about surname frequency as it is about geographical proximity.

A thesis submitted to the Faculty of Medicine University of the Witwatersrand, Johannesburg fulfilment of the requirements for the degree of Philosophy / Seven Y chromosome probes and thirteen restriction enzyme digests were used to examine a conservative estimate of 20000bp, and no new Y-specific polymorphisms were revealed by these systems. The Y chromosome probe 49a, which reveals a Y-specific haplotype with TaqI, was shown to reveal five new complex polymorphisms with Bglll, Hindlll, Pst I, PvuII and Sstl. The new polymorphisms exhibit great genetic diversity, and each enzyme reveals numerous haplotypes, which mostly occur infrequently and are population-specific. The haplotypes for a given enzyme do not correlate strictly with those revealed by the other enzymes, including TaqI, suggesting that each polymorphism results from a combination of restriction site mutations and rearrangement events. Association between the different 49a polymorphisms occurs only in individuals of recent common genetic origin. Y-specific 49a/TagI haplotypes were determined for 933 individuals drawn from 23 different African populations. A total of 31 new haplotypes were observed, some of which contained new alleles or allelic variants. Duplication, in addition to CpG mutation, is implicated in the generation of certain allelic variants. Cluster analysis of genetic distances between populations was calculated using the 49a/TagI haplotype frequencies. Y-specific 49a/TagI haplotype analysis of individual populations was not sufficiently sensitive to accurately distinguish between the different Bantu-speaking Negroid tribal groups. Cluster analysis of larger groupings was more stable, and with the exception of the Khoisan, resulted in a basic split between African and non-African populations. The linkage disequilibrium of the XY275 MspI Y-linked polymorphism was determined. The high allele was generally found in association with the Y chromosome, but the Y-associated low allele was found to occur in Bantu-speaking Negroids, Khoisan-speaking Negroids, the Khoisan, two groups of mixed ancestry, and the Caucasoid South African Asiatic Indian population. The discovery of Y-associated low alleles in non-African as well as African populations suggests that more than one Y chromosome gave rise to the present-day non-African population. The pDP31/EcoRI, p21Al/TagI and Y Alu polymorphisms were also studied in several southern African populations. The pDP31 duplication occurred at high frequencies in Caucasoids, and could be used to indicate Caucasoid male gene flow into hybrid populations. The p21Al/TagI point mutation showed no distinct trends in frequency in the different populations, and several Taql mutations are proposed to have occurred in the repeat unit recognized by this sequence. The Y Alu polymorphism occurred infrequently in Caucasoids, at intermediate frequency in the Khoisan, and at high frequency in Negroids. The presence of the Y Alu insertion in all three major population groups studied is interpreted to suggest that the insert predates the diversification of Homo sapiens. The relationship between the different Y-linked polymorphisms was determined in the populations studied. The Y Alu polymorphism is believed to have originated once from sequencing data, but such information is not available for the other Y polymorphisms studied. No absolute relationship was observed between the Y Alu polymorphism and the 49a/TagI, XY275 Mspl, pDP31/£coRI and p21Al/TagI polymorphisms. It is suggested that the latter polymorphisms have arisen more than once. / WHSLYP2017