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  • 1
    ISSN: 1437-1596
    Keywords: Key words Y chromosome ; Haplotypes ; Evolution ; Population studies ; Genetic affinities ; STR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Notes: Abstract By means of a multicenter study, a large number of males have been characterized for Y-chromosome specific short tandem repeats (STRs) or microsatellites. A complete summary of the allele frequency distributions for these Y-STRs is presented in the Appendix. This manuscript describes in more detail some of the population genetic and evolutionary aspects for a restricted set of seven chromosome Y STRs in a selected number of population samples. For all the chromosome Y STRs markedly different region-specific allele frequency distributions were observed, also when closely related populations were compared. Haplotype analyses using AMOVA showed that when four different European male groups (Germans, Dutch, Swiss, Italians) were compared, less than 10% of the total genetic variability was due to differences between these populations. Nevertheless, these pairwise comparisons revealed significant differences between most population pairs. Assuming a step-wise mutation model and a mutation frequency of 0.21%, it was estimated that chromosome Y STR-based evolutionary lines of descent can be reliably inferred over a time-span of only 1950 generations (or about 49000 years). This reduces the reliability of the inference of population affinities to a historical, rather than evolutionary time scale. This is best illustrated by the construction of a human evolutionary tree based on chromosome Y STRs in which most of the branches connect in a markedly different way compared with trees based on classical protein polymorphisms and/or mtDNA sequence variation. Thus, the chromosome Y STRs seem to be very useful in comparing closely related populations which cannot probably be separated by e.g. autosomal STRs. However, in order to be used in an evolutionary context they need to be combined with more stable Y-polymorphisms e.g. base-substitutions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0711
    Keywords: Down syndrome ; Prenatal screening ; Biochemical markers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Serum samples from 320 women with chromosomally normal fetuses and from 50 women with fetuses affected by Down's syndrome were assayed retrospectively for human chorionic gonadotropin (hCG), pregnancy-specificβ 1 glycoprotein (SP1), alpha fetoprotein (AFP), and unconjugated estriol (uE3) between 14 and 21 weeks of gestation. Nonparametric discriminant analysis was applied to calculate Down syndrome risks on the basis of various combinations of serum parameters. At a risk threshold that falsely identifies 5% of controls as being affected, 46 to 48% of Down syndrome pregnancies were detected by combinations of hCG/AFP, hCG/AFP/uE3, and hCG/AFP/uE3/SP1 respectively. HCG, AFP, and uE3 were assayed in 652 serum samples from women who underwent amniocentesis because of maternal age (≥35 years in this prospective study). 49% of women with euploid fetal karyotype, 8 of 10 pregnancies with Down's syndrome, and 3 pregnancies with sex chromosomal anomalies were identified as being at an increased risk (〉1:380).
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1569-8041
    Keywords: breast cancer ; genetic counselling ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background:With the identification of genes predisposing tohereditary breast cancer, the accurate and consistent estimation of a woman'srisk of developing breast cancer based on her family history is of paramountimportance if national service guidelines are to be developed. Patients and methods:The residual lifetime risk of developingbreast cancer was estimated for 200 women attending a breast cancer geneticassessment clinic by three different methods currently in use in the UK. Riskswere computed on the basis of the Cancer and Steroid Hormone (CASH) study dataand were classified as ‘low/moderate’ (〈20%) or ‘high’(〉20%). These risk categories are representative of those currentlyused to allocate surveillance and genetic testing. Risks were then comparedto estimates derived by other methods used in current clinical practice,including those of Houlston and Murday. Results:The CASH data-based method ascribed 27% to thehigh risk category, as compared to 53% for the combined Houlston andMurday methods. A method based on the number of affected relatives aloneascribed only 14% to the high risk category. Overall, 108 (54%)women were placed in the same risk category by all three methods. Conclusions:This study demonstrates that there is a significantdegree of variability between methods currently used to estimate breast cancerrisk which has serious implications for individual patient management, serviceprovision and multicentre studies evaluating the benefits of genetic testingfor breast cancer susceptibility.
    Type of Medium: Electronic Resource
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