China
Africa
Explore chapters and articles related to this topic
Metabolism and Toxicity of Occupational Neurotoxicants: Genetic, Physiological, and Environmental Determinants
Published in Lucio G. Costa, Luigi Manzo, Occupatinal Neurotoxicology, 2020
Stefano M. Candura, Luigi Manzo, Anna F. Castoldi, Lucio G. Costa
Genetic factors also determine important intersubject variations in the metabolism and neurotoxicity of ethanol and industrial alcohols.38,39 ADH is a dimeric enzyme whose subunit chains are determined by at least six genetic loci, of which at least two, ADH2 and ADH3, are polymorphic. The isoenzymes vary markedly in their kinetic properties, and the frequency of the alleles encoding them vary across ethnic group.54 Both polymorphic ADH loci have been localized to the long arm of chromosome 4.55 ALDH is present in at least four forms, whose characteristics and activity vary substantially.56 Acetaldehyde oxidation is mostly catalyzed by ALDH2, encoded by a gene localized to chromosome 12.57 In Asians and American Indians, a null allele at the ALDH2 locus causes impaired elimination of acetaldehyde and flushing reactions following ingestion or inhalation of relatively small amounts of ethanol. The null allele is dominant, and heterozygotes exhibit ALDH deficiency.38
Naturally Occurring Polymers—Animals
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
We now move to what makes a single egg/sperm combination grow into a child. It is a combination of special events of which we will look at only one aspect. The machinery to construct a person is found about our chromosomes. One cluster of these developmental genes is found in the middle of chromosome 12. Within these genes is a grouping of homeotic genes that reside in the same general area. These genes are called the Hox genes and affect the parts of the body in the exact sequence that they appear in the fruit fly—mouth, face, top of head, neck, thorax, front half of abdomen, rear half of abdomen, and finally the other parts of the abdomen. Also, found in each of these homeotic genes is the same sequence of about 180 base pairs long that is believed to act as a switch to turn on or turn off each gene referred to as the homeobox. Mice were examined and also found to have such homeotic genes and homeoboxes. Mice have 39 Hox genes in four clusters with some differences, but many similarities, with the fruit fly. We have the same Hox clusters as mice with one such cluster, Cluster C, on chromosome 12. A practical implication is that all the work done with other species, such as the fruit fly, may be useful as we look at our own genome with at least such developmental genes.
Putting a Cell Together
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
A different view, called a Circos diagram (circos.ca),7 of the detailed genetic relationships between organisms is diagrammed in Figure 7.4. The complete set of chromosomes of two hypothetical organisms, A and B, form the upper and lower halves of the circle, respectively. Organism A has 26 chromosomes and A, 23. In the arc formed by each numbered chromosome is the complete DNA sequence of that chromosome. Identical or similar sequences are indicated by lines connecting the chromosomes of A and B. If only a short sequence runs are identical, the width of the connecting line is small. If long runs are identical or identical but reversed, the line is wide. The chromosome numbering in this diagram is such that if the genes on one chromosome are in reverse order of those on the other chromosome, the connecting band would be uniform in width. If the sequence order is not reversed, the connecting band must show a constriction point midway, so as to properly connect to the other chromosome. (Diagrams are often constructed so that reverse identity shows the constriction.) If there are no similar sequences on the organisms, there would be no connections in the diagram. In Figure 7.4, chromosomes 1 to 6 of the two organisms are apparently identical. Chromosomes 10 and 11 are reverse-identical. Chromosome 14 of organism A is reverse-identical to chromosome 12 of B. Small regions of chromosomes 15–17 of A connect to chromosomes 7–9 of B, although B chromosomes 7 and 8 also have connections to A chromosomes 22–25. The lack of connections between much of the rest of the chromosomes of A and B in this imagined example would suggest that while part of the phenotypes are the same, much is quite different. For comparisons between real organisms, see reference 7.
Discovery of genetic risk factors for disease
Published in Journal of the Royal Society of New Zealand, 2018
Many genetic effects on gene regulation act in multiple tissues. However, some effects are tissue specific and not all tissues are well represented in GTEx. Specific projects supplement these results and it is important to consider the tissue or tissues relevant to each disease in following up the GWAS ‘hits’. For example, the causes for initiation of lesions in endometriosis are unknown. It is thought that the likely source of cells is endometrial tissue (the tissue lining the inside of the uterus) that ascends into the peritoneum via retrograde menstruation (Giudice 2010; Fung et al. 2015). We are studying genetic control of gene expression in endometrial tissue for follow-up studies in endometriosis (Fung et al. 2015) and have identified evidence for endometriosis associated SNPs influencing expression of the long non-coding RNA LINC00339 and CDC42 on chromosome 1 (Powell et al. 2016) and VEZT on chromosome 12 (Holdsworth-Carson et al. 2016).