DNA repair systems are essential for the maintenance of genome integrity. Consequently, the disregulation of repair genes can be expected to be associated with significant, detrimental health effects, which can include an increased prevalence of birth defects, an enhancement of cancer risk, and an accelerated rate of aging. Although original insights into DNA repair and the genes responsible were largely derived from studies in bacteria and yeast, well over 125 genes directly involved in DNA repair have now been identified in humans, and their cDNA sequence established. These genes function in a diverse set of pathways that involve the recognition and removal of DNA lesions, tolerance to DNA damage, and protection from errors of incorporation made during DNA replication or DNA repair. Additional genes indirectly affect DNA repair, by regulating the cell cycle, ostensibly to provide an opportunity for repair or to direct the cell to apoptosis. For about 70 of the DNA repair genes listed in Table I, both the genomic DNA sequence and the cDNA sequence and chromosomal location have been elucidated. In 45 cases single-nucleotide polymorphisms have been identified and, in some cases, genetic variants have been associated with specific disorders. With the accelerating rate of gene discovery, the number of identified DNA repair genes and sequence variants is quickly rising. This report tabulates the current status of what is known about these genes. The report is limited to genes whose function is directly related to DNA repair.

SummaryThe rates of consanguinity among the parents of babies born in Israel during 1955‐57 were estimated by screening the maternity wards. First‐cousin marriages ranged between 1 and 2 % in Ashkenazic Jews, while the majority of the other Jewish communities exhibited far higher rates of consanguinity.There is little basis for the assumption that the incidence of cousin marriages in Jewish groups reflects the sizes of the isolates in the diaspora. The non‐randomness of such unions finds expression in the distinct preference for marriages between the children of like‐sexed sibs.Cousin marriages between persons originating from different countries testify to some amount of gene flow, which occurred in the recent past between the different groups in the diaspora.Among several ethnic groups, the marriages concluded after immigration to Israel exhibit a trend towards declining consanguinity rates. While this tendency might merely indicate the break‐up of the smaller isolates, which have hitherto existed within the communities, a process of merging between these larger units has also set in on a very large scale. Ashkenazic Jews originating from different countries intermarry at an increasing rate. At present only a minority of persons belonging to the smaller Ashkenazic groups choose partners of identical origin. Around 10 % of Ashkenazic Jews contract marriages with members of the other communities. Intercommunity marriages between the various non‐Ashkenazic congregations are also very common.A rough estimate of the genetic risk involved in consanguineous unions was obtained by comparing the mean numbers of live children after different durations of marriage in cousin families and others. In two out of five such comparisons, the cousin families exhibited a small but significant disadvantage. However, no difference in family size could be detected between mothers, who are offspring of first cousins and all other mothers in the sample.We are greatly indebted to Dr Shaul Merin, who participated in some of the field work during this survey. In the sorting and evaluation of the data we were assisted by Fredy Gruber, Sarah Rapaport, Navah Bloch and Elisheva Barak.It is a pleasure to acknowledge the courtesy and co‐operation of the medical authorities and the nursing staff of the following maternity wards: Rambam Government Hospital, Haifa; Rothschild Municipal Hospital, Haifa; Hadassah Municipal Hospital, Hakirya, Tel‐Aviv; Governmental Hospital, Tsahalon Division, Jaffa, T.A.; Beilinson Hospital, Petah‐Tiqwa; Hadassah University Hospital, Jerusalem; Bikur Holim General Hospital, Jerusalem; Shaarei Tzedek, General Hospital, Jerusalem.We are also much obliged to Prof. R. Bachi, Director of the Central Bureau of Statistics, Government of Israel, for consultations and references.

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which is more suitable for studies of DNA synthesis in vitro than the single mutant strain U2355pol IIPs (DNA polymerase III").

Identification of a geomorphic index to represent lower thresholds for minor flows in ephemeral, alluvial streams in arid environments is an essential step as a precursor for reliable flash flood hazard estimations and establishing flood warning systems. An index, termed Alluvial wadi Flood Incipient Geomorphologic Index (AFIG), is presented. Analysis of data from an extensive field survey in the arid ephemeral streams in southern and eastern Israel was conducted to investigate the AFIG and the control over its value across the region. During the survey we identified distinguishable flow marks in the lower parts of streams' banks, such as niches, vegetation line, and change in bank material, which are indicative of low flows. The cross-sectional characteristics of the AFIG were studied in relationship with contributing drainage basin characteristics such as lithology, topography, and precipitation. Drainage area and hardness of the exposed lithology (presented as a basin-wide index) are the preferred descriptors to be used in estimating a specific AFIG in unsurveyed sites. Analyses of discharge records from seven hydrometric stations indicate that the recurrence interval of the determined AFIG is equal to or more frequent than 0.5 yr