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A significant proportion of both pericentric and paracentric inversions have recurrent breakpoints and so could either have arisen through multiple independent events or be identical by descent (IBD) with a single common ancestor. Of two common variant inversions previously studied, the inv(2)(p11q13) was genuinely recurrent while the inv(10)(p11.2q21.2) was IBD in all cases tested. Excluding these two variants we have ascertained 257 autosomal inversion probands at the Wessex Regional Genetics Laboratory. There were 104 apparently recurrent inversions, representing 35 different breakpoint combinations and we speculated that at least some of these had arisen on more than one occasion. However, haplotype analysis identified no recurrent cases among eight inversions tested, including the variant inv(5)(p13q13). The cases not IBD were shown to have different breakpoints at the molecular cytogenetic level. No crossing over was detected within any of the inversions and the founder haplotypes extended for variable distances beyond the inversion breakpoints. Defining breakpoint intervals by FISH mapping identified no obvious predisposing elements in the DNA sequence. In summary the vast majority of human inversions arise as unique events. Even apparently recurrent inversions, with the exception of the inv(2)(p12q13), are likely to be either derived from a common ancestor or to have subtly different breakpoints. Presumably the lack of selection against most inversions allows them to accumulate and disperse amongst different populations over time. [ABSTRACT FROM AUTHOR]

Background Congenital chromosome abnormalities are relatively common in our species and among structural abnormalities the most common class is balanced reciprocal translocations. Determining the parental origin of de novo balanced translocations may provide insights into how and when they arise. While there is a general paternal bias in the origin of non-recurrent unbalanced rearrangements, there are few data on parental origin of non-recurrent balanced rearrangements. Methods The parental origin of a series of de novo balanced reciprocal translocations was determined using DNA from flow sorted derivative chromosomes and linkage analysis. Results Of 27 translocations, we found 26 to be of paternal origin and only one of maternal origin. We also found the paternally derived translocations to be associated with a significantly increased paternal age (p<0.008). Conclusion Our results suggest there is a very pronounced paternal bias in the origin of all non-recurrent reciprocal translocations and that they may arise during one of the numerous mitotic divisions that occur in the spermatogonial germ cells prior to meiosis. [ABSTRACT FROM AUTHOR]

Summary: Background: Turner syndrome, one of the most common cytogenetic abnormalities, is characterised by complete or partial X-chromosome monosomy. Cancer risks in women with Turner syndrome have not been clearly established. We aimed to compare the risk of cancer in women with this syndrome with that of the general population. Methods: We formed a national cohort of 3425 women who were cytogenetically diagnosed with Turner syndrome in Great Britain between 1959 and 2002. Identifying information for these patients was sent to the National Health Service Central Register (NHSCR) for England and Wales and to the NHSCR for Scotland. Individuals who were identified on this register were followed-up for cancer incidence. Standardised incidence ratios (SIRs) and 95% CIs were calculated on the basis of the number of cancers observed compared with that expected based on national incidence rates. Cumulative risk estimates were obtained by use of the Kaplan-Meier method. Findings: A total of 58 299 person-years were accrued during the study, with a mean of 17·0 years (SD 8·6) follow-up per patient. 73 malignancies other than non-melanoma skin cancer occurred (SIR 0·9 [95% CI 0·7–1·2]). Risks were significantly increased for tumours of the CNS (n=13; 4·3 [2·3–7·4]), especially for meningioma (n=7; 12·0 [4·8–24·8]) and childhood brain tumours (n=3; 10·3 [2·1–30·1]), and for cancers of the bladder and urethra (n=5; 4·0 [1·3–9·2]) and eye (n=2; 10·5 [1·3–37·9]), compared with the general population. However, the risk of breast cancer was significantly decreased (n=10; 0·3 [0·2–0·6]). The SIR for cutaneous melanoma was 2·2 (95% CI 1·0–4·4; n=8), and one of the ocular cancers was a melanoma. The risk of corpus uteri cancer was significantly increased at ages 15–44 years (n=3; 8·0 [1·6–23·2]). During follow-up, five women, all with a Y-chromosome lineage, developed gonadoblastoma of the ovary, corresponding to a cumulative risk of 7·9% (95% CI 3·1–19·0) by age 25 years in this group. Interpretation: This study shows that, in addition to having an increased risk of gonadoblastoma, women with Turner syndrome seem to be at increased risk for meningioma and childhood brain tumours, and possibly bladder cancer, melanoma, and corpus uteri cancer, but are at a decreased risk for breast cancer. Reasons for these risks might relate to genetic and hormonal factors or to the effects of hormonal treatments given to women with Turner syndrome. [Copyright &y& Elsevier]