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Hereditary and Metabolic Diseases of the Central Nervous System in Adults
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Gene frequency depends on the population. For HEXA, the carrier rate is 1:25–30 in Ashkenazi Jews, 1 per 2500–3600 prior to carrier screening. The carrier rate for Louisiana Cajun, French Canadian, and Pennsylvania Dutch populations is 1:50. The carrier rate for most populations is 1:250–1:300. Prevalence is 1 per 309,000 live births. For GM2A, the gene frequency is unknown.
Population aspects of genetic counselling and genetic screening
Published in Angus Clarke, Alex Murray, Julian Sampson, Harper's Practical Genetic Counselling, 2019
Conversely, fragmentation and isolation of populations combined with inbreeding, as seen in some minority migrant populations, are likely to increase the incidence of autosomal recessive disorders, even when the parent population does not have a particularly high frequency of deleterious genes. Again, it is not the gene frequency but the frequency of affected homozygotes that is increased. Prolonged inbreeding over many generations might in theory actually ‘breed out’ harmful recessive genes by progressively eliminating them as homozygotes. However, this would require much suffering over many generations – longer than the current social arrangements are likely to persist. This would not be a helpful course to recommend prospectively, and there is no evidence that it has actually occurred in inbred populations. While the precise effects on gene and phenotype frequencies are thoroughly analysed in a number of books on population genetics, the moral for the clinician is to be wary of generalisations, and to realise that in the great majority of situations the advice given to individual couples may have a profound effect on them and their offspring but will rarely alter the population structure to a significant extent.
Cell division
Published in Frank J. Dye, Human Life Before Birth, 2019
Environmental changes, such as an increase in ultraviolet light, climate change, and so on, will affect some members of a population more than others. In other words, some will survive and others will not. Those who have genes that allow them to adapt will persist, whereas the others will not live to reproduce and their genes will be eliminated. This change in the gene frequency of a population is what we call evolution.
An update on current and potential genetic insights and diagnosis of Alport syndrome
Published in Expert Opinion on Orphan Drugs, 2020
Alport syndrome is a genetic disorder of basement membranes resulting from pathogenic variants in the collagen IV genes COL4A3, COL4A4 and COL4A5. The major clinical manifestations of Alport syndrome are hematuria, progressive kidney disease frequently resulting in kidney failure (i.e., the need for dialysis or kidney transplantation), sensorineural deafness, and ocular anomalies. The disorder derives its name from Cecil Alport, who established the association of hematuric kidney disease and hearing loss in a large English kindred in the 1920 s [1]. Alport syndrome is a rare disorder, although incidence and prevalence are somewhat uncertain. The gene frequency in the United States has been estimated to be 1 in 5000–10,000 [2]. Alport syndrome accounts for about 2% of children undergoing kidney transplantation in the United States and 1–2% of children with chronic kidney disease [3,4]. According to the USRDS 2007 Annual Report, the incidence of kidney failure caused by Alport syndrome was 0.5–0.6 per million population while the prevalence was 6.8 per million population [5].
Analysis of Common β-Thalassemia Mutations in North Vietnam
Published in Hemoglobin, 2018
Lan Thi Thuong Vo, Trang Thu Nguyen, Hai Xuan Le, Ha Thi Thu Le
Table 2 summarizes the prevalence and percentage of the heterozygous and homozygous states of the β-thal mutations investigated in this study. The four studied mutations were detected in 203/244 patients (83.2%) (Table 2). The most common mutation was codon 26 (G>A) resulting in Hb E, found in 128/244 thalassemia patients (52.46%), including only one patient carrying the homozygous state. The presence of Hb E was detected in 129 alleles accounting for 26.4% of gene frequency. The codon 26 mutation was also detected in 9/152 healthy people (5.9%), with a 3.0% gene frequency. The mutations at the codons 41/42 and 17 were detected in 90 (36.89%) and 78 (31.97%) patients, respectively, of which the homozygous state of the codons 41/42 and codon 17 mutations were found in five (2.05%) and two (0.82%) patients, respectively. Thus, the gene frequencies of these two mutations were 19.4 and 16.4%, respectively. Each of these mutations was separately detected in three (1.0% gene frequency) healthy people. In particular, the heterozygous mutation at codon 95, which is known to be specific for Vietnamese people, was detected in three patients (0.6% gene frequency) and one healthy person. The frequencies of the four investigated β-thal mutations are shown in Table 3 in comparison with previous reports on β-thal in different regions of Vietnam and neighboring countries.
Thalassemia Status in Cambodia
Published in Hemoglobin, 2022
With regard to the prevalence of hemoglobinopathies in Cambodia, about 40.0% (range 30.0–50.0%) of the general population were estimated to be carriers, of which 1.0% carry β-thalassemia (β-thal) [at least 4.8 million are carriers, 48,000 are β-thal major (β-TM) sufferers] [4–6]. The overall prevalence of β-thal and α-thalassemia (α-thal) were 40.9 and 39.6%, respectively [7]. The estimated annual birth rate of thalassemic patients is about 2240 births for β-TM. Currently, the specific epidemiological data regarding the abnormal gene frequency/mutations among different ethnic groups is unknown. A high prevalence of genetic hemoglobin (Hb) disorders exists in Cambodia (Table 1) [7].