Forensic genetic laboratories perform an increasing amount of genetic analyses of the X chromosome, in particular to solve complex cases of kinship analysis. For some biological relationships X-chromosomal markers can be more informative than autosomal markers, and there are a large number of markers, methods and databases that have been described for forensic use. Due to their particular mode of inheritance, and their physical location on a single chromosome, some specific considerations are required when estimating the weight of evidence for X-chromosomal marker DNA data. The DNA Commission of the International Society for Forensic Genetics (ISFG) hereby presents guidelines and recommendations for the use of X-chromosomal markers in kinship analysis with a special focus on the biostatistical evaluation. Linkage and linkage disequilibrium (association of alleles) are of special importance for such evaluations and these concepts and the implications for likelihood calculations are described in more detail. Furthermore it is important to use appropriate computer software that accounts for linkage and linkage disequilibrium among loci, as well as for mutations. Even though some software exist, there is still a need for further improvement of dedicated software.

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This report summarizes the current knowledge with respect to genetic changes associated with the development of prostate cancer. The relation between the occurrence of these changes and the stage of the disease is by far not clear yet, albeit that some tendencies become more or less evident. In Fig. 2 these are summarized. Whereas changes on 7q and loss or gain of the X chromosome are not consistently found by either RFLP or ISH analysis, other changes are (8p-, 10p-, 10q, 16q-, and 18q-). Clearly the picture is far from complete and even more the relevant genes on these chromosomes are not defined. E-cadherin was considered a good candidate and indeed the value as progression marker is great. However, the studies so far indicate that E-cadherin does not behave as a classical type I suppressor gene and the relation with 16q loss remains to be established. The data available to date regarding chromosomal changes in prostate cancer are limited. Many studies have to be pursued to identify the consistent changes, and moreover, to map the relevant loci harbouring the genes that are implicated in the development of this disease. This knowledge will be critical in the design of appropriate diagnostic methods and possibly clues towards therapy.

The following guidelines were adopted by an Ad Hoc Committee convened at the Fourth International Workshop on the Fragile X Syndrome and X-Linked Mental Retardation to establish minimum cytogenetic standards for the preparation and analysis of the fragile X chromosome. The intention of the committee was to develop and provide practical standards for the routine cytogenetic detection of the fragile X. The guidelines describe reasonable criteria for effective tissue culture methods for eliciting the Xq27.3 fragile site in vitro and for the analysis of such chromosome preparations.

Nomenclature guidelines are proposed for non-specific and for syndromal forms of X-linked mental retardation. Non-specific mental retardations (MRX) are given unique symbols for each family (MRX1, MRX2, MRX3 ...). Syndromal mental retardations (MRXS) which do not as yet have specific symbols are given unique interim symbols for each syndrome (MRXS1, MRXS2, MRXS3 ...). The prerequisite for assignment of serial MRX and MRXS gene symbols is a minimum lod score (or multipoint lod score) of +2 between the MR locus and one or more X chromosome markers. Prior approval of availability for proposed gene symbols must be obtained from the Nomenclature Committee of the Human Gene Mapping Workshops.