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Environmental Disease
Published in Gary S. Moore, Kathleen A. Bell, Living with the Earth, 2018
Gary S. Moore, Kathleen A. Bell
Changes in the number of chromosomes or the structure of them can also produce genetic diseases. These are referred to as cytogenetic defects. Such defects tend not to be inherited, but result from disorders occurring during meiosis, when eggs or sperm are formed in the parent, or when the embryo is developing. These defects involve large parts of the chromosome and most often appear as deletions or additions of chromosome material. Most of these defects are fatal and fail to survive embryonic development. About 20 percent of fetuses that spontaneously die while in the uterus have this type of genetic defect. There are survivable cytogenetic disorders, however, and one of the more recognizable is trisomy 21. Trisomy 21 or Down’s disease is characterized by the addition of an extra chromosome to chromosome number 21, which is expressed phenotypically as various degrees of mental retardation, predisposition to leukemia, congenital heart disease, and characteristic facial features including epicanthal folds of the eyelids causing an oriental appearance of the eyes, flat nose or absent bridge, and low-set ears.
Population dynamics
Published in A. W. Jayawardena, Environmental and Hydrological Systems Modelling, 2013
Division of cells is by binary fission, mitosis, and meiosis. Prokaryotic cells that lack a nucleus divide by binary fission. Eukaryotic cells divide by mitosis or meiosis. Mitosis is nuclear division followed by division of the cell called kinesis. The cell duplicates the chromosomes in its nucleus to generate two identical daughter cells. Both these processes are asexual. Meiosis is the process of reduction division in which the number of chromosomes per cell is cut in half. Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes, including single-celled organisms that reproduce sexually. In diploid cells, specialized cells called gametes (egg and sperm) are created through meiosis. Then, the sperm and egg join together to form a single cell. Cell growth cycle is a hot area of research because of its medical applications. Cancer cells grow exponentially, and an understanding of the growth cycle is needed to control their proliferation through drugs.
Genetic toxicology
Published in Chris Winder, Neill Stacey, Occupational Toxicology, 2004
In germinal tissues, eukaryotic chromosomes undergo meiosis, when the diploid (2n) chromosome number is reduced to a haploid (n) number, ensuring that each gamete has one copy of each pair of genes. During meiosis, homologous chromosomes (one of paternal origin and one of maternal origin) are paired then assorted independently, and a high level of chromosome recombination may occur; therefore, each gamete carries a discrete complement of genetic traits. Without these processes, genetic variability would be limited to rare mutational events that survive natural selection. Interference with normal meiosis may result in genomic mutations, which are changes in the number of chromosomes, or aneuploidy, and are also referred to as numerical aberrations.
miR-30d-5p represses the proliferation, migration, and invasion of lung squamous cell carcinoma via targeting DBF4
Published in Journal of Environmental Science and Health, Part C, 2021
Yitian Qi, Yi Hou, Liangchen Qi
DBF4 gene (Dumbbell former 4), a regulatory subunit of the Cdc7 kinase, plays a key role in DNA replication,10 replication check-point activation,11 meiosis,12,13 trans-lesion synthesis,14,15 histone homeostasis,16 and mitotic exit.17 Originally discovered in the search for DNA synthesis mutants in brewer’s yeast, DBF4 has been shown to be involved in the initiation of DNA replication.11,18DBF4 is currently found to be an oncogene in some kinds of cancers.19 A study has demonstrated the increased expression of DBF4 in NSCLC cells and tissue, suggesting that it may play a carcinogenic role in NSCLC,20 but its function in LUSC is not clear.
Gene drive to reduce malaria transmission in sub-Saharan Africa
Published in Journal of Responsible Innovation, 2018
Austin Burt, Mamadou Coulibaly, Andrea Crisanti, Abdoulaye Diabate, Jonathan K. Kayondo
In Aedes mosquitoes there is a naturally occurring driving Y chromosome (or, more accurately, a driving male-determining region of a chromosome) that, in some crosses, leads to more than 90% male progeny. The underlying molecular mechanism has not yet been reported, but cytogenetically, drive is associated with breakage of the X chromosome at male meiosis (Newton, Wood, and Southern 1976). This led to the hypothesis that if a nuclease that specifically recognises and breaks the X chromosome can be expressed during meiosis, then that might lead to preferential transmission of the Y chromosome and a male bias (Figure 7). Proof-of-principle demonstration of this route to drive in A. gambiae was reported by Galizi et al. (2014), who showed that expression of an engineered variant of the PpoI nuclease from a slime mold, expressed during spermatogenesis using the B2-tubulin promoter sequences, led in some lines to males producing 95% male offspring. The PpoI enzyme recognises a sequence in the ribosomal RNA-encoding repeat, which, fortuitously, is found only on the X chromosome in A. gambiae.
Hazard characterization of silver nanoparticles for human exposure routes
Published in Journal of Environmental Science and Health, Part A, 2020
In summary, mature sperm cells are the most sensitive target of AgNPs in the reproductive system, followed by the spermatogenesis including the disturbance on meiosis of secondary spermatocytes and differentiation of spermatogonia cells. An upstream sensitivity level to AgNPs was reported during spermatogonia.