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Basic Chemical Hazards to Wildlife
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
The sum of genes in a population is called the gene pool and we are just beginning to appreciate the value of a gene pool even though we have selectively bred animals and plants for agriculture, sports, and aesthetical purposes for thousands of years. Each individual being carries two copies of each gene, one set from each parent. Variations of these sets of genes are called alleles. Individuals having two identical alleles are homozygous for the gene and those having different alleles are heterozygous for the gene. The individual’s genotype is the specific assortment of alleles he or she possesses. According to the Hardy-Weinberg law, even though the alleles for each gene are passed from parents to offspring in various combinations, the overall frequency of appearance for a given allele remains constant in a population. In other words, genetic equilibrium resists change in the population. Selection pressures can skew this equilibrium though and that is where the hazard assessor fits in, because COCs as toxins are one among other pressures working against genetic equilibrium. Other anthropogenic pressures are deforestation, desertification, acid rain, global warming, and ozone depletion.
Is Supraphysiological Enhancement Possible, and What are the Downsides?
Published in Steven Kornguth, Rebecca Steinberg, Michael D. Matthews, Neurocognitive and Physiological Factors During High-Tempo Operations, 2018
Naturally occurring genetic mutations remind us that enhanced capabilities come with consequences. For example, brain wiring in savants that results in supernormal skills with arithmetic and memory seems to come hand-in-hand with deficient psychosocial skills (Treffert and Christensen 2006). One current explanation is that abnormal cognitive processing that involves intense “restricted and repetitive behaviors” is an alternate cognitive strategy that results from a deficiency in awareness of self not present in so-called neurotypical (“normal”) individuals (Vital, Wallace and Happe 2009). The plasticity of the brain permits compensation for some extreme differences that permit survival but invariably produce other changes. In another example, sickle cell trait is protective against malaria, providing an overall advantage to populations in a malarial environment but including a subset of individuals homozygous for sickle cell trait who pay the price for the greater survival advantage of the group in the form of painful and disabling sickle cell disease (Aidoo et al. 2002). Significant shifts in physiological balance to produce special advantages appear to be accompanied by health risks and other compensatory deficits. The military should never be so anxious to be the earliest adopter of a new and incompletely tested “bright idea” that they end up providing the experimental evidence for why it was actually a bad idea.
DNA Structure, Sequencing, Synthesis, and Modification: Making Biology Molecular
Published in Richard J. Sundberg, The Chemical Century, 2017
When a person inherits the mutated gene from both parents (homozygous) they are susceptible to the condition. The mutation is particularly high in regions of Africa that are heavily infested with malaria. Heterozygous individuals are to some extent protected from the effects of malaria. The same mutation is found in areas of South India with a high incidence of malaria. The protection provided by the mutation reinforces the protection provided by developed immunity to malaria and increases the likelihood of survival to adulthood. There is also a developmental aspect to the relationship between hemoglobin status and survival of malaria. The fetal form of hemoglobin is not subject to the mutation and new born infants are not susceptible to the sickle cell condition until about age 2, when the hemoglobin content shifts to the adult version. Subsequently, a number of other hemoglobin mutations have been identified and related to particular conditions and syndromes. For examples, there are high levels of mutations in β-hemoglobin in parts of the world (Mediterranean, Southeast Asia) that lead to β-thalassemia, which, like sickle cell anemia, affects the oxygen-carrying capacity of hemoglobin.
Advance intervention of recessive ill-conditioned feature: the early-stage design method based on system recessive inheritance
Published in Journal of Engineering Design, 2023
Zifeng Nie, Peng Zhang, Fang Wang
In biology, inheritance can be divided into dominant inheritance and recessive inheritance. Dominant inheritance is controlled by dominant genes. On homologous chromosomes, when two homologous dominant genes exhibit in pairs, or when dominant and recessive genes integrate as alleles, dominant traits will appear. Recessive inheritance indicates that the parents carry certain genes that do not show the trait explicitly. When these genes are passed on to the offspring, the recessive traits may be triggered to be dominant when the recessive genes are homozygous. In the genetic process of organisms, recessive inheritance plays a significant part in view of that the exhibition of some rare traits in organisms is often related to the manifestation of homozygous recessive genes, as shown in Figure 2(a). A recessive gene will not incur an ill-conditioned trait when the allele is dominant. Even in the course of multiple generations, this kind of ill-conditioned traits is hidden. Only if a pair of recessive genes become alleles during the process of inheritance, that is homozygous for the recessive gene, will the ill-conditioned traits incurred by the recessive gene exhibit distinctly. It is notable that most of the recessive ill-conditioned features that appear in organisms are ensured by homozygosity of recessive genes (Clark and Pazdernik 2013; Nambisan 2017; Wahlsten 2019).