A detailed comparative Y-chromosome map between the white-cheeked gibbon (Nomascus leucogenys) and human

• Autor(a) principal: Felício, Sara Inácio
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10348/8760

The species on which this study will focus is the white-cheeked gibbon, Nomascus leucogenys, a member of the Hylobatidae family, which currently faces imminent extinction along with other gibbon species. Gibbons exhibit an astonishingly higher tempo of large-scale chromosomal rearrangements which are up to 20 times that of the average rate in mammals. Still, a satisfactory explanation is yet to be uncovered as to why gibbons experienced such an accelerated rate of evolution and how such a high number of chromosomal rearrangements could become fixed in such a relatively short time. Gibbons represent a key node in the primate phylogeny given their intermediate branching position between Old World monkeys and great apes. Representing a unique viewpoint for the study of the origins of hominoid characteristics, they have been described as astoundingly flexible and adaptable because they have prospered through times of grave global and local climate and sea level oscillations while other hominoid lineages perished. Most cytogenetic studies on gibbons have focused on their karyotypes and have provided little or no information on the Y chromosome. The objective of this study is to produce a comparative Y chromosome map between N. leucogenys and human using fluorescent in situ hybridization (FISH) - a rapid, sensitive and powerful technique based on the hybridization between a fluorescently labelled probe and a complemental cytological target. With this goal in mind, 15 bacterial artificial chromosomes (BACs) derived from human Y chromosome and a human α-Sat DNA sequence were selected and hybridized to gibbon’s metaphase spreads and extended chromatin fibres, ultimately leading to the construction of a comparative map. Given the small size of the gibbon Y chromosome, as well as the inability to find an optimized fibre-FISH protocol suitable for mapping human Y BACs onto extended chromatin fibres of the gibbon, it was not possible to determine the accurate order of the DNA sequences in question. However, it was possible to produce a comparative map showing the rough location of 15 BACs from the human Y chromosome in the N. leucogenys counterpart, 12 of them containing important Y-linked genes. The results provide compelling evidence for occurrence of evolutionary intrachromosomal rearrangements that resulted in the change of gene order on the human and gibbon Y chromosomes.