Recessive mutation

Heavy metals possess mutagenic effect. The assessment of mutagenic effect was assessed through evaluation of genes recessive mutation frequency in the micronucleus in oral mucous cells of children living at the tested areas (Tabl. 3). 

Figure 11-1-4. Recurrence Risk for the Mating of Two Heterozygous Carriers (Aa) of a Recessive Mutation...

Normal females have two copies of the X chromosome, so they usually require two copies of the mutation to express the disease. However, because X inactivation is a random process, a heterozygous female will occasionally express an X-linked recessive mutation because, by random chance, most of the X chromosomes carrying the normal allele have been inactivated. Such females are termed manifesting heterozygotes. Because they usually have at least a small population of active X chromosomes carrying the normal allele, their disease expression is typically milder than that of a hemizygous male. 

Both types of muscular dystrophy are X-linked recessive mutations, making a gain-of-function highly unlikely for either type (choice A). 

Assuming random mating, the Hardy-Weinberg principle specifies a predictable relationship between gene and genotype frequeicies in populations. It can be applied to estimate the frequency of heterozygous carriers of an autosomal recessive mutation. 

The incidence of Duchenne muscular dystrophy in North America is about 1/3,000 males. On the basis for this figure, what is the gene frequency of this X-linked recessive mutation ... 

Answer A. Because males have only a single X chromosome, each affected male has one copy of the disease-causing recessive mutation. Thus, the incidence of an X-linked recessive disease in the male portion of a population is a direct estimate of the gene frequency in the population. 

Severe combined immune deficiency (SCID) is a rare inherited disorder in which multiple components of the immune system are affected. About 50% of SCID cases are caused byX-linked recessive mutations in the gene encoding a subunit of a receptor for interleukins 2,4,... 

The phenotypic complexity noted for other GCPR diseases is true also for PTHRl mutations. Opposite clinical manifestations have been reported to result from distinct recessive mutations in the gene. These rare variants present as Eiken syndrome, a distinct entity from JMC and Blomstrand s chondrodysplasia and from enchondromatosis. The skeletal features are opposite those in Blomstrand s chondrodysplasia. The Eiken syndrome variant, resulting in a truncation at position 485, may result in a paradoxical phenotype caused by the consequences of disrupting the carboxyl tail of the receptor (60). 

Duchatelet, S., Ostergaard, E., Cortes, D., Lemainque, A., and Juher, C. (2005) Recessive mutations in PTHRl cause contrasting skeletal dysplasias in Eiken and Blomstrand syndromes. Hum. Mol. Genet. 14, 1-5. 

Autosomal recessive mutations in the 17/3-hydroxysteroid dehydrogenase (17/3HSD) 3 gene impair the formation of testosterone in the fetal testis and give rise to genetic males with female external genitalia. Such individuals are usually raised as females, but virilize at the time of expected puberty as the result of increases in serum testosterone. More than 14 mutations have now been identified [20]. 

BH4 deficiency can be caused by mutations in genes encoding the enzymes involved in its biosynthesis (GTPCH, PTPS, and SR) or regeneration (PCD/DCoH and DHPR). BH4 deficiency due to autosomal recessive mutations in BH4-metabo-lizing enzymes (except SR) has been described as a cause of hyperphenylalaninemia (HPA) [6]. Biochemical, clinical, and DNA data of patients with BH4 deficiencies are tabulated in the BIODEF and BIOMDB databases and are available on the Internet (www.bh4.org) [7]. Depending on the enzyme defect and the mode of inheritance,... 

Carbon tetrachloride was not mutagenic in bacteria. It induced intra-chromosomal and mitotic recombination but not aneuploidy in Saccharomyces cerevisiae, aneuploidy was detected in another single study in Aspergillus nidulans. In vivo, in a single study with Drosophila melanogaster, no sex-linked recessive mutations were observed. 

DMX, Drosophila melanogaster, sex-linked lethal recessive mutations DIA, DNA strand breaks/cross-links, L1220 mouse leukaemic... 

If a mutation is lethal, a homozygote will not survive and will be lost in an early (and usually undetected) spontaneous abortion. Healthy individuals carry as many as ten lethal recessive mutations as well as at least 3-5 autosomal recessive mutations of a seriously harmful type. Harmful dominant mutations are also frequent in the population. These include an elevated lipoprotein content of the blood and an elevated cholesterol level which are linked to early heart disease. 

Cancerous Cells Are Genetically Abnormal Some Tumors Arise from Genetically Recessive Mutations... 

A number of tumors arise from recessive mutations in which the mutations appear to be in growth-control genes. 

Alcalai, R., Metzger, S., Rosenheck, S., Meiner, V., and Chajek-Shaul, T. (2003). A recessive mutation in desmoplakin causes arrhythmogenic right ventricular dysplasia, skin disorder, and woolly hair./. Am. Coll. Cardiol. 42, 319-327. 

Norgett, E. E., Hatsell, S. J., Carvajal-Huerta, L., Cabezas, J. C., Common, J., Purkis, P. E., Whittock, N., Leigh, I. M., Stevens, H. P., and Kelsell, D. P. (2000). Recessive mutation in desmoplakin disrupts desmoplakin-intermediate filament interactions and causes dilated cardiomyopathy, woolly hair, and keratoderma. Hum. Mol. Genet. 9, 2761-2766. 

Camacho Vanegas, O., Bertini, E., Zhang, R. Z., Petrini, S., Minosse, C., Sabatelli, P., Giusti, B., Chu, M. L., and Pepe, G. (2001). Ullrich scleroatonic muscular dystrophy is caused by recessive mutations in collagen Type VI. Proc. Natl. Acad. Sci. USA 98, 7516-7521. 

The gene mutation test systems in mice include the specific locus test, in which wild-type treated males are crossed with females carrying recessive mutations for visible phenotypic effects. The F progeny have the same phenotype as the wild-type parent unless a mutation, corresponding to a recessive mutant marker, has occurred. Such tests... 

Two types of inherited disorders caused by mutations of genes related to BH4 are known. Autosomal dominant mutations in the GCH gene are causative for DOPA-responsive dystonia (DRD) [157,158]. Malignant hyperphenylalaninemia or atypical phenylketonuria (PKU) is caused by recessive mutations of genes encoding BH4-biosynthetic or recycling enzymes [159]. 

Isobe, K., Ito, S., Hosaka, H., Iwamura, Y., Kondo, H., Kagawa, Y., and Hayashi, J. I., Nuclear-recessive mutations of factors involved in mitochondrial translation are responsible for age-related respiration deficiency of human skin fibroblasts. J. Biol. Chem. 273, 4601-4606 (1998). 

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