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Cytogenetics of the fragile (X) syndrome and a discussion of possible mechanisms involved in its cause.

Haslam, J. S. (1987) Cytogenetics of the fragile (X) syndrome and a discussion of possible mechanisms involved in its cause. Doctoral thesis, University of Surrey (United Kingdom)..

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The aims of this project were threefold; to produce a reliable method for demonstrating the fragile(X) site in human chromosomes; to perform pedigree studies to ascertain the inheritance of the syndrome and its association with mental retardation; and to shed light on underlying cytological mechanisms involved. In a pilot study, leucocyte cultures from a few known fragile(X) patients were grown under a variety of conditions. The results were analysed for the fragile(X) site, the quality of chromosome morphology and the mitotic index. Three culture conditions were chosen and used to grow blood samples from individuals with non-specific mental retardation along with a standard culture acting as a control. Out of two hundred and fifty samples forty one were demonstrated to have the fragile(X) site including five out of six obligate carriers. The majority of the positive cases were detected by the modified culture conditions, although three were only detected by the control method. The method demonstrating the greatest proportion of cells with a fragile(X) site was not the same in each case; it was thus concluded that more than one method should be used in screening for the fragiIe(X) site. The results indicate that there is a considerable increase in autosomal fragile sites in individuals with the fragile (X ) site. The autosomal fragile sites were widely distributed throughout the chromosome complement. Possible mechanisms for the fragile(X) syndrome are discussed. A hypothesis is advanced, postulating a faulty gene in the thymidine synthetase pathway which results in lowered thymine production in fragile(X) individuals, the thymine being replaced in the DNA by other bases. It is suggested that fragile sites on autosomes arise from a failure of mitotic coiling due to impaired binding of chromosomal proteins to altered base sequences. The location of the gene responsible for the fragile(X) syndrome is discussed, as is its possible role in causing mental retardation.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Haslam, J. S.
Date : 1987
Contributors :
Additional Information : Thesis (M.Phil.)--University of Surrey (United Kingdom), 1987.
Depositing User : EPrints Services
Date Deposited : 22 Jun 2018 13:01
Last Modified : 06 Nov 2018 16:52

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