NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …

sources and effects of ionizing radiation

http://www.jbc.org/content/267/1/166.full.pdf

8-Hydroxyguanine, an abundant form of oxidative DNA damage, causes G----T and A----C substitutions.

https://mmbr.asm.org/content/mmbr/48/1/60.full.pdf

Mutagenesis and inducible responses to deoxyribonucleic acid damage in Escherichia coli.

Microsatellites, or tandem simple sequence repeats (SSR), are abundant across genomes and show high levels of polymorphism. SSR genetic and evolutionary mechanisms remain controversial. Here we attempt to summarize the available data related to SSR distribution in coding and noncoding regions of genomes and SSR functional importance. Numerous lines of evidence demonstrate that SSR genomic distribution is nonrandom. Random expansions or contractions appear to be selected against for at least part of SSR loci, presumably because of their effect on chromatin organization, regulation of gene activity, recombination, DNA replication, cell cycle, mismatch repair system, etc. This review also discusses the role of two putative mutational mechanisms, replication slippage and recombination, and their interaction in SSR variation.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-294X.2002.01643.x

Microsatellites: genomic distribution, putative functions and mutational mechanisms: a review.

A functional c-myb gene is required for normal murine fetal hepatic hematopoiesis.

https://www.cell.com/cell/pdf/0092-8674(90)90719-U.pdf

Hypervariable minisatellite DNA is a hotspot for homologous recombination in human cells

THE availability of DNA molecules of known sequence and rapid methods for the determination of the sequence of particular DNA fragments1–3 make it possible to investigate the molecular action of mutagens and carcinogens more closely4,5. For example, there is considerable evidence that some types of lesion in DNA such as UV light-induced pyrimidine dimers and various chemical adducts are blocks to DNA synthesis both in vivo6–9 and in vitro10,11. The available data support the hypothesis that the block occurs at the level of the lesion on the template strand10,11. We have used DNA containing such lesions on a template of known sequence for in vitro DNA synthesis by DNA polymerase 1 to investigate the site of the block at the level of the nucleotide sequence. This method allows us to determine both the site at which lesions capable of blocking synthesis by DNA polymerase occur and exactly where synthesis stops in relation to the lesion.

Sites of inhibition of in vitro DNA synthesis in carcinogen- and UV-treated phi X174 DNA.

Tracts of the alternating dinucleotide polydeoxythymidylic-guanylic [d(TG)].polydeoxyadenylic-cytidylic acid [d(AC)], present throughout the human genome, are capable of readily forming left-handed Z-DNA in vitro. We have analyzed the effects of the Z-DNA motif d(TG)30 upon homologous recombination between two nonreplicating plasmid substrates cotransfected into human cells in culture. In this study, the sequence d(TG)30 is shown to stimulate homologous recombination up to 20-fold. Enhancement is specific to the Z-DNA motif; a control DNA fragment of similar size does not alter the recombination frequency. The stimulation of recombination is observed at a distance (237 to 1,269 base pairs away from the Z-DNA motif) and involves both gene conversion and reciprocal exchange events. Maximum stimulation is observed when the sequence is present in both substrates, but it is capable of stimulating when present in only one substrate. Analysis of recombination products indicates that the Z-DNA motif increases the frequency and alters the distribution of multiple, unselected recombination events. Specifically designed crosses indicate that the substrate containing the Z-DNA motif preferentially acts as the recipient of genetic information during gene conversion events. Models describing how left-handed Z-DNA sequences might promote the initiation of homologous recombination are presented.

The Z-DNA motif d(TG)30 promotes reception of information during gene conversion events while stimulating homologous recombination in human cells in culture.

In vitro DNA synthesis on a phi X174 template primed with a restriction fragment and catalyzed by the Escherichia coli DNA polymerase I large (Klenow) fragment (pol I) terminates at the nucleotide preceding a site that has been altered by ultraviolet irradiation or treatment with N-acetylaminofluorene. Termination on ultraviolet-irradiated templates is similar when synthesis is catalyzed by E. coli DNA polymerase III holoenzyme (pol III), phage T4 DNA polymerase, a polymerase alpha from human lymphoma cells, or avian myeloblastosis virus reverse transcriptase. 3' leads to 5' exonuclease activity cannot be detected in the reverse transcriptase and DNA polymerase alpha preparations. On N-acetylaminofluorene templates, pol I, pol III, and T4 polymerase reactions terminate immediately preceding the lesion, whereas reverse transcriptase-catalyzed reactions and, at some positions in the sequence, polymerase alpha-catalyzed reactions terminate at the site of the lesion. Substitution of Mn2+ for Mg2+ changes the pattern of pol I-catalyzed termination sites. The data suggest that termination is a complicated process that does not depend exclusively on the 3' leads to 5' exonuclease activity associated with many polymerases.

Sites of termination of in vitro DNA synthesis on ultraviolet- and N-acetylaminofluorene-treated phi X174 templates by prokaryotic and eukaryotic DNA polymerases

Peter D. Moore

Papers

Hypervariable minisatellite DNA is a hotspot for homologous recombination in human cells

Sites of inhibition of in vitro DNA synthesis in carcinogen- and UV-treated phi X174 DNA.

The Z-DNA motif d(TG)30 promotes reception of information during gene conversion events while stimulating homologous recombination in human cells in culture.

Sites of termination of in vitro DNA synthesis on ultraviolet- and N-acetylaminofluorene-treated phi X174 templates by prokaryotic and eukaryotic DNA polymerases

The role of DNA polymerase in base substitution mutagenesis on non-instructional templates.