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Cytogenetic analysis using C-banding, silver staining and fluorescent staining was carried out on a population sample of Poecilia Iatipinna derived from Tampico, Mexico, to verify the presence of sex chromosomes in individuals from the southern areas of this species range and to investigate the extent of C-band and Ag-NOR polymorphisms. Females were found to have W heteromorphic chromosomes, with large amounts of heterochromatin-rich in AT nucleotide sequences. C-banding corresponded to the pattern proposed as typical for the genus. Specimens share one of the Ag- NOR locations previously described in populations from the U.S.A. and show additional ones as well.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

The origin and geographical distribution of mammalian species (my examples are lemurs and bats) correlate with predictable chromosomal structural changes (KFT=karyotypic fission theory). Chromosome studies provide information about fertility between individuals and they are significant for identification of the geographical origin of reproductive isolation within mammal families. Each family predictably has chromosome sets with numbers that range from one to double the lowest number of chromosomes. The chromosome numbers of all species within a single family are used to reconstruct that family’s evolutionary geographical dispersion. Polymorphic chromosome numbers (that is a range such as 34, 35, 36, 37, and 38) in a single population indicate the location where chromosomal diversification arose. Chromosome numbers of descending order correlate with relative distance from fission epicenters as the fissioned chromosomes gradually spread to neighboring populations. Furthermore, the location of chromosomal diversification (that is “karyotypic fission events) is associated with geographical “zones of transition” (after Professor R.W. Wilkie). My analysis, mapped one (Lepilemuridae) of the five families of lemurs (Class Mammalia, Order Primates, sub-order Lemuridae). The origin of this family’s diversification is here hypothesized to have occurred at an ecological transition zone in Northern Madagascar between a humid evergreen-forest that extends to the East relative to a dry deciduous forest along the West Coast. My analysis of Vespertilionidae (insectivorous bats representing one third of all bat species) suggests a diversification event occurred in Asia; South China. Geographical distribution is important in the formation of biological diversity. A single species can inhabit a wide range and exhibit great diversity that is brought about by natural selection. The Holarctic reindeer found in Scandinavia, Russia, China, Canada and Alaska (including caribou) are all a single species Rangifertarandus that exhibits variation in size and in coat pattern, changes brought about by adaptive selection by the environment or human selective breeding but they all have 70 similar chromosomes and they are all reproductively compatible. There is a single species of reindeer. Although, there is measurable DNA sequence divergence; there has been no “speciation” as these circumpolar cervids are genetically compatible.

The research presented in this dissertation consists of four papers that revolve around the structure of human chromosomes and their relationship to birth defects. A new technique is described to produce spiralization of human metaphase chromosomes. The important feature is heat followed by trypsin treatment. By varying conditions, it is possible to produce bands, spirals and intermediate states. An investigation of human metaphase chromosomes reveals identical lateral bands in sister chromatids when stained with Quinacrine mustard or Giemsa-trypsin. A hybrid of these two methods produces banding patterns which are different in sister chromatids yet may be repeated in homologous chromatids. A case study is presented in which a 3l-year old white female with a history of ovarian dysfunction and infertility delivered a male infant with trisomy 13. Her cultured leucocytes were mosaic for trisomy X. The natures of trisomy X and trisomy 13 are discussed with particular emphasis on the genetic transmission. In another case study of a family, it is found that some individuals who completely lack dermal ridges are mosaic for an extra X chromosome with deletions in both arms. A mechanism is proposed to account for the extra chromosome. / Ph. D.

Adult CBA mice at 0, 50, 73, and 90 percent levels of inbreeding were used to study variation's in chromosome number from bone marrow cells. Chromosome counts were made from 20 animals at each level of inbreeding except at the 73 percent level where only 13 animals were available. The chromosome number was determined for 24 countable cells per animal at each level, and used to determine if there were significant differences in the variation of chromosome number among the various levels of inbreeding. A modal class of 40N chromosomes was noted for the mice in all groups. However, there was considerable variation within each group. The average percentages of abnormal counts were 23.5 for the controls, 37.9 for the 50 percent inbred level, 28.3 for the 73 percent inbred level and 27.7 for the 90 percent inbred level. An analysis of variance indicated a significant difference between the various levels of inbreeding for the percentage of normal cells. Duncan's Multiple Range Test indicated that the major coutribution to the significant F-ratio came from the 50 percent level of inbreeding. Consequently, the relationship is not linear, but the higher level of abnormal cells occurred at or below the 50 percent level of inbreeding with a decreasing number of abnormal cells at the higher levels. / Master of Science

Master of Science