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Radiation-Induced Genetic Damage
Published in Kedar N. Prasad, Handbook of RADIOBIOLOGY, 2020
These studies show that ionizing radiation can induce deletion, duplication, and rearrangement of chromosomes. The incidence of small deficiency and duplication may be higher than gross rearrangements at lower radiation doses.2 Zygotes carrying larger deficiency and duplication may be lost because of high genetic imbalance.
Sex Chromosome Anomalies
Published in Merlin G. Butler, F. John Meaney, Genetics of Developmental Disabilities, 2019
L. Hamerton John, A. Evans Jane
Examples of patients with sex chromosome tetrasomy and pentasomy (48,XXXX, 49,XXXXX, 48,XXYY, 48,XXXY, 49,XXXXY, 49,XXXYY, 48,XYYY, 49,XYYYY) are rare and have been reviewed recently by Linden et al. (124) (Fig. 5). In general, patients with multiple sex chromosome anomalies are more severely affected than trisomic individuals. The fact that all of these patients survived gestation and that sex chromosome polysomies are not found in any significant numbers among spontaneous abortions indicates a lower level of genetic imbalance than that found in autosomal trisomies, the majority of which are eliminated during gestation. Presumably, this is due to inactivation of all the X chromosomes in excess of one. All of these patients have been ascertained as clinical referrals due to their disabilities. This results in a potential for ascertainment bias towards more severely affected patients. These are rare conditions occurring in fewer than 1 in 10,000 births and, in some cases, perhaps as low as 1 in 100,000 births.
Chemical Carcinogenesis as a Consequence of Alterations in the Structure and Function of DNA
Published in Philip L. Grover, Chemical Carcinogens and DNA, 2019
In the case of xeroderma pigmentosum, the genetic imbalance seems to contribute to what Burnet50 calls “intrinsic” mutagenesis, possibly by affecting the mutation process in the cells of these individuals.51 It is not yet known if other DNA-repair-deficient syndromes, as well as other genetic deficiencies that lead to chromosomal aberrations (i.e., Bloom’s syndrome), contribute to “intrinsic” mutagenesis on the structural gene or on the chromosomal level. On the other hand, genetic influence on cancer predisposition, which does not contribute to “intrinsic” mutagenesis by altering either the amount or rate of DNA damage or repair (i.e., initiation), might be conceptualized as “extrinsic” mutagenesis (i.e., altering the expression of genes or promotion).
Chemopreventive efficacy of juniper berry oil (Juniperus communis L.) on azoxymethane-induced colon carcinogenesis in rat
Published in Nutrition and Cancer, 2021
Turan Yaman, Ahmet Uyar, Ahmet Ufuk Kömüroğlu, Ömer Faruk Keleş, Zabit Yener
Oxidative stress plays an important role in the molecular mechanism of cancer development and progression (79). For instance, free radicals, which can directly damage DNA or increase the genetic imbalance of affected cells, can form in the first phase of neoplastic transformation, called initiation (80). It has been reported that oxidative radicals are the factors that contribute to the formation of cancer, invasion, and metastatic spread (19). The development of colorectal cancer is directly attributed to the activation of oxidative stress pathways in the intestinal lumen, which manifests by increasing the number and magnitude of aberrant crypt focies (81). AOM induces colon cancer in experiment animals via a mechanism in which the mediator is GSH exhaustion and the total antioxidant capacity in the colon cells of rats is impaired (82). It has been revealed that increasing the activities of antioxidant enzymes (SOD and CAT) reduces AOM-induced colon cancer in animals, which reduces oxidative stress and plays an important role in the mechanism of chemopreventive effects (82). In chemopreventive treatment, an increase was observed in antioxidant enzyme activity induced by antitumor agents (83).
Recent advances in screening and diagnosis of hemoglobinopathy
Published in Expert Review of Hematology, 2020
Kanjaksha Ghosh, Kinjalka Ghosh, Reepa Agrawal, Anita H. Nadkarni
Similarly, heterozygotes of beta-thalassaemias with coinheritance of multiple (more than 4) copies of normal alpha gene produce the necessary genetic imbalance of alpha and beta-globin chains required for clinical expression of the disease as thalassemia syndrome [5]. For more than half of a century, many techniques were developed in the laboratory to define various hemoglobinopathies. Some of these tests have lost relevance today, while few others continue to be used in various laboratories of the world [6].