Codominant Mendelian Inheritance Research Articles

Novel and Broadly Applicable Microsatellite Markers in Identified Chromosomes of the Philippine Dengue Mosquitoes, Aedes aegypti (Diptera: Culicidae).

Dengue is the leading arboviral infection in the Philippines. Its endemicity in the country is due to the presence of its primary mosquito vector, Aedes aegypti (L.). This species has limited microsatellite markers. This study characterized microsatellite markers screened in silico from intergenic regions of the updated reference genome of Ae. aegypti from Liverpool, U.K. Criteria for good markers are: polymorphic, inherited in a Mendelian codominant manner, no null alleles, selectively neutral, randomly associated, and broadly applicable across different regions. Genotypes were scored using ABI Peak Scanner and were screened for the presence of null alleles. Hardy-Weinberg equilibrium, linkage disequilibrium, and robustness of the markers were determined by GENEPOP using Ae. aegypti samples from selected highland and lowland sites (n = 30 each) in the Philippines and outgroups (Thailand and Vietnam). Mendelian codominant inheritance was examined using F1 offspring of Ae. aegypti family (n = 30 each) derived from samples collected from Cebu city highlands and Maramag, Bukidnon. From the 63 randomly selected markers, nine were polymorphic. Two markers (Aaeg1-3D of chromosome 1 and Aaeg3-4C of chromosome 3) satisfied all criteria, hence, are good broadly useful microsatellite markers. Two other markers (Aaeg2-2E of chromosome 2 and Aaeg3-2A of chromosome 3) met all criteria but deviated from Mendelian codominant inheritance. These new markers of the Philippine Ae. aegypti with their chromosomal locations relative to the other published markers are presented, and will ultimately be useful in a variety of population genetic studies of Ae. aegypti to protect the public health.

Validating a predictive model of cannabinoid inheritance with feral, clinical, and industrial Cannabis sativa.

PremiseHow genetic variation within a species affects phytochemical composition is a fundamental question in botany. The ratio of two specialized metabolites in Cannabis sativa, tetrahydrocannabinol (THC) and cannabidiol (CBD), can be grouped into three main classes (THC‐type, CBD‐type, and intermediate type). We tested a genetic model associating these three groups with functional and nonfunctional alleles of the cannabidiolic acid synthase gene (CBDAS).MethodsWe characterized cannabinoid content and assayed CBDAS genotypes of >300 feral C. sativa plants in Minnesota, United States. We performed a test cross to assess CBDAS inheritance. Twenty clinical cultivars obtained blindly from the National Institute on Drug Abuse and 12 Canadian‐certified grain cultivars were also examined.ResultsFrequencies of CBD‐type, intermediate‐type, and THC‐type feral plants were 0.88, 0.11, and 0.01, respectively. Although total cannabinoid content varied substantially, the three groupings were perfectly correlated with CBDAS genotypes. Genotype frequencies observed in the test cross were consistent with codominant Mendelian inheritance of the THC:CBD ratio. Despite significant mean differences in total cannabinoid content, CBDAS genotypes blindly predicted the THC:CBD ratio among clinical cultivars, and the same was true for industrial grain cultivars when plants exhibited >0.5% total cannabinoid content.ConclusionsOur results extend the generality of the inheritance model for THC:CBD to diverse C. sativa accessions and demonstrate that CBDAS genotyping can predict the ratio in a variety of practical applications. Cannabinoid profiles and associated CBDAS segregation patterns suggest that feral C. sativa populations are potentially valuable experimental systems and sources of germplasm.

Preliminary results of SSR based characterization of sour (Prunus cerasus L.) and sweet cherry (Prunus avium L.) genotypes cultivated in Hungary

Cherry cultivation in the Carpathian basin area began more than 100.000 years ago. Adapting to the basin specific ecological conditions resulted in high degree of genetic variability among the cherry cultivars. The SSR (Simple Sequence Repeat) markers allow the discrimination of the cultivars and determination their specific DNA fingerprints. Due to the high degree of polymorphism of microsatellite markers, generally only six SSR loci are enough to differentiate the varieties. Microsatellite markers are used not only for cultivar identification but also for the verification of synonyms and homonyms. Owing to their locus specificity and Mendelian codominant inheritance, parentage can be clearly identified, primary and secondary relationships between the cultivars can be discovered. The aim of this research was to characterize 29 sour cherry (Prunus cerasus L.), and 38 sweet cherry (Prunus avium L.) genotypes cultivated in Hungary to establish their DNA fingerprints in 6 SSR loci by allele numbers and sizes.

GENETIC CHARACTERISTICS AND DISTANCES AMONGST SPANISH AND FRENCH RABBIT POPULATIONS

A total of 990 rabbits were tested using 18 blood electrophoretic markers. These animals belong to 6 breed populations presently breed in Spain (Spanish Common, Spanish Giant, Butterfly, Burgandy Fawn, New Zealand White and Californian), one Spanish cross-breed population, three French crossbreed populations originated from the INRA selected lines (1077, 2066 and 9077) and one Wild Spanish population. 12 markers were found to be polymorphic (Dia-2, 6-Pgd, Es-1, Es-2, Es-3, Es-7, Ada, Hp, Tf, Ca-2 and Hb), each one being controlled by one locus and showing autosomal co-dominant Mendelian inheritance. We have found large differences in gene frequencies of Dia-2, 6-Pgd, Ada, Es- 1, Es-2 and Es-3 loci in French populations. The genetic variabiliy estimated using the average degree of heterozygosity was lower in French than in Spanish populations. The results obtained from genetic distance analysis showed differences between French and Spanish populations. France 3 was the most divergent population. The genetic distance values obtained revealed that French populations are as different amongst themselves as they are between Spanish populations (the value obtained was corresponding to subspecie, NEI, 1987). These differences could have originated from the high selectiva pressure applied to parental lines. In the Spanish group, Spanish Giant was the most divergent population.

6-phosphogluconate dehydrogenase (Pgd-1) in the rat and its possible linkage

6-phosphogluconate dehydrogenase polymorphism between inbred strains of rats is demonstrated. The biochemical marker exists in two allelic forms, and the trait shows a codominant mendelian inheritance. From gene mapping in different species, there is evidence for linkage between Pgd-1 and the known coat color locus, brown, in linkage group II.

Evaluation of genetic diversity of Iranian grapevine accessions using microsatellite markers

Introduction: Grapevine (Vitis vinifera L.) is economically the most important fruit crop in the world. There are 8,000 to 10,000 grape cultivars existing worldwide today. Characterization and determination of grapevine cultivars are sometimes difficult using conventional methods. Molecular approaches might be implemented in cultivar identification and breeding programs, since morphological markers are time-consuming and prone to equivocal interpretations (MARGIT et al. 2005). The high polymorphism of microsatellites (or SSR simple sequence repeats), a special class of tandem repeat loci involving a base motif of 1-6 bp of DNA repeated up to 100 times, allows cultivar identification, and their co-dominant Mendelian inheritance allows the reconstruction of crosses (VOUILLAMOZ et al. 2003).

Power of Microsatellite Markers for Analysis of Genetic Variation and Parentage Verification in Sheep

We report the genetic analysis of 100 individuals of an elite breeding flock of Afshari sheep with a selected set of eighteen microsatellite markers. A full characterization of this set of eighteen loci was carried out generating allele frequency distributions that were used to estimate the genetic information content of these loci, including genetic variability, inbreeding, individual and parent verification parameters. Disregarding MCMA26 monomorphic pattern, microsatellite loci showed moderate level of polymorphism, as such totally 102 alleles were detected with a mean number of 6 alleles per locus. The average expected heterozygosity was 0.72 (SD = 0.07) and the average Polymorphism Information Content (PIC) was 0.67 (SD = 0.08). Total value of inbreeding based on marker data was estimated as -0.02 so it indicates that inbreeding occurred less than would be expected at random. The overall probability of identity considering all twelve independent loci combined was 3.148E-13 meaning lower than 1 in 31 trillions. The results of this study indicate, despite the selective breeding and closed flock system over a number of generations, a relatively high level of heterozygosity still exists in the representative sheep flock. The high degree of multiallelism and the clear and simple codominant Mendelian inheritance of the set of microsatellites used provide a powerful system for the unique identification of Afshari sheep individuals for fingerprinting purposes and parentage testing.

Power of Microsatellite Markers for Fingerprinting and Parentage Analysis in Eucalyptus grandis Breeding Populations

We report the genetic analysis of 192 unrelated individuals of an elite breeding population of Eucalyptus grandis (Hill ex Maiden) with a selected set of six highly polymorphic microsatellite markers developed for species of the genus Eucalyptus. A full characterization of this set of six loci was carried out generating allele frequency distributions that were used to estimate parameters of genetic information content of these loci, including expected heterozygosity, polymorphism information content (PIC), power of exclusion, and probability of identity. The number of detected alleles per locus ranged from 6 to 33, with an average of 19.8 +/- 9.2. The average expected heterozygosity was 0.86 +/- 0.11 and the average PIC was 0.83 +/- 0.16. Using only three loci, it was possible to discriminate all 192 individuals. The overall probability of identity considering all six EMBRA microsatellite markers combined was lower than 1 in 2 billion. An analysis of the sample size necessary to estimate expected heterozygosity with minimum variance indicated that at least 64 individuals have to be genotyped to characterize this parameter with adequate accuracy for most microsatellites in Eucalyptus. The high degree of multiallelism and the clear and simple codominant Mendelian inheritance of the set of microsatellites used provide an extremely powerful system for the unique identification of Eucalyptus individuals for fingerprinting purposes and parentage testing.

Highly polymorphic microsatellite markers in Chamaecyparis obtusa

Nine microsatellite loci in hinoki, Chamaecyparis obtusa (Sieb. et Zucc.) Endl., were identified and characterized. A genomic library, developed using enrichment with magnetic beads, was screened to identify microsatellite repeats (CT/AG). The microsatellite loci, where the alleles were segregated, displayed codominant Mendelian inheritance. Genetic analysis of 16 plus trees and two unrelated individuals of Chamaecyparis obtusa revealed that all loci were highly polymorphic, with an average of 10.3 alleles per locus, and an average gene diversity of 0.77. The applicability of these microsatellite loci was also tested in other species of the Cupressaceae and in Cryptomeria japonica (L.f.) D. Don (Taxodiaceae, a family closely related to Cupressaceae). Polymerase chain reaction (PCR) amplification was successful for about half of the loci of the species in the genus Chamaecyparis. However, the PCR amplification patterns of the 11 species of Cupressaceae showed no clear correlations with their molecular phylogeny. The highly polymorphic microsatellite loci in Chamaecyparis obtusa, identified here, will be useful in studies of hinoki breeding and population genetics.

A major gene effect on fasting insulin and insulin sensitivity in familial combined hyperlipidemia.

The most common inherited dyslipidemia, familial combined hyperlipidemia (FCHL), is associated with insulin resistance. Whether insulin sensitivity in these families is inherited is not known. Therefore, we investigated the inheritance of insulin sensitivity in 352 nondiabetic family members from 37 families with FCHL, 105 of whom had undergone testing using the hyperinsulinemic-euglycemic clamp technique for the measurement of insulin sensitivity. First, complex segregation analysis of fasting insulin levels (both unadjusted and age-, age(2)-, and BMI-adjusted) was used for modeling of the variance in fasting insulin levels. In these analyses, Mendelian codominant inheritance (P = 0.320 for unadjusted and P = 0.295 for adjusted insulin values) was not rejected over the most general model and fit the data significantly better than the sporadic model (P < 0.001). Polygenic and environmental models were rejected (P < 0.001). The Mendelian codominant model explained 44 and 45% of the variance in unadjusted and adjusted fasting insulin levels, respectively. The proposed genotypes of this locus, based on segregation analysis, were associated with directly measured insulin sensitivity in 105 FCHL family members who underwent the hyperinsulinemic-euglycemic clamp (P < 0.001). These results provide evidence for a major gene regulating insulin sensitivity in FCHL families. Possible pleiotropic effects of this insulin sensitivity locus on dyslipidemias in FCHL remain to be elucidated.

Genetic segregation analysis of autonomic nervous system dysfunction in families of probands with idiopathic congenital central hypoventilation syndrome

Idiopathic congenital central hypoventilation syndrome (CCHS) is a very rare syndrome with major respiratory complications. Hypothesizing that CCHS is the most severe manifestation of general autonomic nervous system dysfunction (ANSD), we applied a case-control family study design to investigate the genetics of ANSD. Fifty-two probands with CCHS were identified, as well as 52 age-, race-, and gender-matched controls. ANSD phenotypic features were characterized in the cases, controls, and their family members. Our earlier studies found that most ANSD symptoms were more likely in CCHS cases and their relatives than in controls and their relatives (P < 0.05). The goal of the current study was to determine if the familiality of ANSD was consistent with a genetic pattern. We performed major locus segregation analysis of ANSD utilizing regressive models. CCHS probands were assumed to be affected; controls and relatives were designated as affected if they had two or more relevant symptoms. The hypothesis of "no transmission and no familial effects" was rejected in both case and control families. Case families were consistent with transmission of a major effect; control families were not (the difference in the pattern of results was significant, P < 0.0001). In the total data set, the best-fitting model was codominant Mendelian inheritance of a major gene for ANSD. These case-control family studies support our hypothesis that CCHS is the most severe manifestation of a general ANSD, with a family pattern consistent with Mendelian transmission, and demonstrate the potential utility of the approach to studies of other, similarly intractable disorders.

Microsatellite analysis of maternal half-sib families of Quercus robur, pedunculate oak: detection of seed contaminations and inference of the seed parents from the offspring

Microsatellites were used for genetic analysis of maternal half-sib families of Quercus robur, pedunculate oak, a highly outcrossing tree species. A model half-sib family including the mother tree and 28 offspring individuals as well as samples from six single tree harvests from a forestry company, 4–8 individuals each, were genotyped at 9 microsatellite loci. No prior information about the genotypes of the mother trees were available for these six seedlot samples. Analysis of the model half-sib family revealed that the maternal genotypes can be inferred from the offspring genotypes due to codominant Mendelian inheritance of the microsatellites. Analysis of the single tree harvests, supplied as six maternal half-sib families, revealed contaminations with unrelated seedlings in four out of six cases. Average relatedness between the remaining individuals indicated that they were indeed half-sibs, probably with a proportion of full-sibs among them. For five samples the genotypes of the mother trees were partially inferred from the offspring genotypes. The supposed number of five different mother trees was confirmed by direct comparison of the maternal genotypes and by pairwise FST calculations between families. We show that correct genotype reconstruction can be confirmed by monitoring recombination events between linked markers. Our results demonstrate that microsatellite analysis is a suitable means to approach two key problems of legal regulations on the marketing of seed material from pedunculate oak: the number of trees included in seed harvests and the detection of seed contaminations.

A Common Genetic Mechanism Determines Plasma Apolipoprotein B Levels and Dense LDL Subfraction Distribution in Familial Combined Hyperlipidemia

Familial combined hyperlipidemia (FCH) is a common lipid disorder characterized by elevations of plasma cholesterol and/or triglyceride in first-degree relatives. A predominance of small, dense LDL particles and elevated apolipoprotein B (apoB) levels is commonly found in members of FCH families. Many studies have investigated the genetic mechanisms determining individuals' lipid levels, in FCH families. Previously, we demonstrated a major gene effect on LDL particle size and codominant Mendelian inheritance involved in determination of apoB levels in a sample of 40 well-defined FCH families. An elevation of apoB levels is associated metabolically with a predominance of small, dense LDL particles in FCH. To establish whether a common gene regulates both traits, we conducted a bivariate genetic analysis to test the hypothesis of a common genetic mechanism. In this study, we found that 66% of the total phenotypic correlation is due to shared genetic components. Further bivariate segregation analysis suggested that both traits share a common major gene plus individual polygenic components. This common major gene explains 37% of the variance of adjusted LDL particle size and 23% of the variance of adjusted apoB levels. Our study suggests that a major gene that has pleiotropic effects on LDL particle size and apoB levels may be the gene underlying FCH in the families we studied.

Segregation analysis of cutaneous melanoma in Queensland.

To investigate whether the familial clustering of cutaneous melanoma is consistent with Mendelian inheritance of a major autosomal gene, maximum likelihood segregation analyses were performed in a population-based sample of 1,912 families ascertained through a proband with melanoma diagnosed in Queensland between 1982 and 1990. Analyses were performed with the S.A.G.E. statistical package, using the REGTL program for a binary trait with a variable age of onset. We sought medical confirmation for all family members reported to have had melanoma, and only medically verified cases among relatives were included in the analyses. The hypothesis of codominant Mendelian inheritance gave a significantly better fit to the data than either dominant or recessive Mendelian inheritance, or environmental transmission. Overall, both Mendelian inheritance of a single major gene, and purely environmental transmission were rejected (P < 0.001). In both the single major gene and environmental models, there was strong evidence of familial dependence in melanoma occurrence (P < 0.001). These results are consistent with reported genetic heterogeneity in melanoma inheritance and suggest that other familial factors, such as pigmentation, skin type, and sun exposure habits, may play an important role in the familial clustering of melanoma.

Segregation analysis of cutaneous melanoma in Queensland

To investigate whether the familial clustering of cutaneous melanoma is consistent with Mendelian inheritance of a major autosomal gene, maximum likelihood segregation analyses were performed in a population-based sample of 1,912 families ascertained through a proband with melanoma diagnosed in Queensland between 1982 and 1990. Analyses were performed with the S.A.G.E. statistical package, using the REGTL program for a binary trait with a variable age of onset. We sought medical confirmation for all family members reported to have had melanoma, and only medically verified cases among relatives were included in the analyses. The hypothesis of codominant Mendelian inheritance gave a significantly better fit to the data than either dominant or recessive Mendelian inheritance, or environmental transmission. Overall, both Mendelian inheritance of a single major gene, and purely environmental transmission were rejected (P < 0.001). In both the single major gene and environmental models, there was strong evidence of familial dependence in melanoma occurrence (P < 0.001). These results are consistent with reported genetic heterogeneity in melanoma inheritance and suggest that other familial factors, such as pigmentation, skin type, and sun exposure habits, may play an important role in the familial clustering of melanoma. Genet. Epidemiol. 15:391–401,1998. © 1998 Wiley-Liss, Inc.

Genetic analysis of the freshwater crayfish Cherax tenuimanus.

The marron (Cherax tenuimanus) is one of the few species of freshwater crayfish native to Australia that is suitable for aquaculture and occurs only in the southwest of Western Australia. This study describes polymorphic microsatellite markers which differentiate marron populations from several geographically distinct regions (including rivers and streams, dams, and commercial marron farms) throughout Western Australia. Twenty microsatellite loci, primarily of the (CA)n. (GT)n type, were isolated and sequenced from a marron cosmid library. Three of these loci were characterised further. Two loci exhibited extensive polymorphism and one was monomorphic. The polymorphic loci exhibited Mendelian codominant inheritance in the family group comprising two individual parents and approximately 100 offspring bred for this study. These loci permitted differentiation between the five geographically distinct populations studied and thus provide a basis for genetic characterisation of marron stock in Western Australia.

Identification and characterization of a RAPD-PCR marker for distinguishing Asian and North American gypsy moths.

The recent introduction of the Asian gypsy moth (Lymantria dispar L.) into North America has necessitated the development of genetic markers to distinguish Asian moths from the established North American population, which originated in Europe. We used RAPD-PCR to identify a DNA length polymorphism that is diagnostic for the two moth strains. The polymorphism maps to an autosomal locus with codominant Mendelian inheritance. DNA sequence analyses of the Asian and North American forms enabled development of locus-specific primers so that this marker, designated FS-1, will be useful for strain identification under varying conditions in different laboratories.

Microsatellites and PCR genomic analysis.

Microsatellites form a significant proportion of the growing family of repetitive DNA sequences, widely dispersed in the human genome. Due to their ubiquity, PCR (polymerase chain reaction) typability, Mendelian co-dominant inheritance, and extreme polymorphism, microsatellites have assumed an increasingly important role as markers in the genome. Apart from their obvious applications in genome mapping and positional cloning, these markers have been applied in fields as disparate as tumour biology, personal identification, population genetic analysis, and the construction of human evolutionary trees. Microsatellites are associated with human disease, not only as markers of risk but also directly in disease aetiopathogenesis, providing new insights into non-Mendelian inheritance; the replication, repair, and mutation of eukaryotic DNA; the regulation of gene transcription; and protein-protein interactions. These insights have resulted in novel paradigms for oncogenesis and neurological disease.

The evolving technology of DNA fingerprinting and its application to fisheries and aquaculture

In 1985, Alec Jeffreys reported the development of multilocus DNA fingerprinting by Southern blot‐detection of hypervariable minisatellites or variable number of tandem repeat (VNTR) loci. This technology found immediate application to various forensic and scientific problems, including fisheries and aquaculture. By 1989, however, it was recognized by many researchers that inherent problems exist in the application of multilocus fingerprinting to large sample sizes as might occur in fisheries and aquaculture genetic studies. As such, individual VNTRs were cloned for single‐locus DNA fingerprinting. Although single‐locus fingerprinting ameliorates many of the problems associated with multilocus DNA fingerprinting, it suffers from the problem that electrophorectic anomalies of band migration within and between gels necessitates binning of alleles, thus underestimating genetic variability in a given population. Amplification of microsatellite loci by the polymerase chain reaction, however, solved many of the problems of Southern blot‐based DNA fingerprinting. Moreover, microsatellites exhibit attributes that make them particularly suitable as genetic markers for numerous applications in aquaculture and fisheries research: (1) they are abundant in the genome; (2) they display varying levels of polymorphism; (3) alleles exhibit codominant Mendelian inheritance; (4) minute amounts of tissue are required for assay (e.g., dried scales or otoliths); (5) loci are conserved in related species; (6) potential for automated assay. Recent innovations in DNA fingerprinting technology developed over the past 5 years are discussed with special emphasis on microsatellites and their application to fisheries and aquaculture, e.g., behavioural and population genetics of wild species, and selection and breeding programmes for aquaculture broodstock.

Segregation analysis of breast cancer in a population‐based sample of postmenopausal probands: The Iowa women's health study

Inheritance of a major susceptibility gene for breast cancer has been primarily investigated in families with early-onset disease. However, familial clustering of late-onset breast cancer is well documented, and genetic factors may also be relevant. In the Iowa Women's Health Study, we evaluated evidence for a major gene after allowing for measured environmental risk factors. Two hundred sixty-five incident breast cancer probands were identified from a prospective cohort study of 41,837 women aged 55 to 69 years at baseline in 1986. A pedigree development form was mailed to the probands to ascertain all first-degree female relatives. A questionnaire and body measurement protocol were mailed to identified living relatives or surrogates. Segregation analyses were conducted on a total of 1,145 women in 251 families using regressive models as implemented in S.A.G.E. Mendelian codominant inheritance of an allele that produced an earlier-age-at-onset provided the best fit to the data. Incorporation of measured environmental risk factors as covariates yielded no significant improvements in the likelihoods. Approximately 50% of this population could be expected to carry a late-onset breast cancer susceptibility gene, and 23% of the population is susceptible because of the environment in which they live. Homozygous gene carriers are predicted to have a mean age-at-onset of 48 years, over 20 years earlier than heterozygotes; few cases would be expected among non-gene carriers. In conclusion, the transmission pattern of late-onset breast cancer may be determined by a common susceptibility gene.