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At least 55 records · Page 3Linked to original sources
PubMed1976

[Relationship between genetic differentiation of the thymus in mice of different strains and malignant growth. IV. Genetic analysis of the thymic index in mice].

Relative thymus weight was estimated in C3H/He, C57BL/6 mice, their F1 and backcross hybrids, as well as in the progeny of complete diallel crosses between the BALB/c, C3H/He, C57BL/6 and AKR/J strains. On the basis of the analysis of these measurements, a conclusion is drawn that this character is inherited with incomplete dominance of smaller relative weight. The genes determining greater thymus weight are concentrated in the genetic pool of AKR/J and C57BL/6 strains. These genes are characterized by some degree of recessivity with respect to the genes determining smaller thymus weight which are concentrated in the genetic pool of C3H/He and BALB/c strains. The highest concentration of the "plus" and "minus" genes is found in the genetic pools of AKR/J and C3H/He strains respectively.

Animals↗
PubMed1992

The molecular through ecological genetics of abnormal abdomen. IV. Components of genetic variation in a natural population of Drosophila mercatorum.

Natural populations of Drosophila mercatorum are polymorphic for a phenotypic syndrome known as abnormal abdomen (aa). This syndrome is characterized by a slow-down in egg-to-adult developmental time, retention of juvenile abdominal cuticle in the adult, increased early female fecundity, and decreased adult longevity. Previous studies revealed that the expression of this syndrome in females is controlled by two closely linked X chromosomal elements: the occurrence of an R1 insert in a third or more of the X-linked 28S ribosomal genes (rDNA), and the failure of replicative selection favoring uninserted 28S genes in larval polytene tissues. The expression of this syndrome in males in a laboratory stock was associated with the deletion of the rDNA normally found on the Y chromosome. In this paper we quantify the levels of genetic variation for these three components in a natural population of Drosophila mercatorum found near Kamuela, Hawaii. Extensive variation is found in the natural population for both of the X-linked components. Moreover, there is a significant association between variation in the proportion of R1 inserted 28S genes with allelic variation at the underreplication (ur) locus such that both of the necessary components for aa expression in females tend to cosegregate in the natural population. Accordingly, these two closely linked X chromosomal elements are behaving as a supergene in the natural population. Because of this association, we do not believe the R1 insert to be actively transposing to an appreciable extent. The Y chromosomes extracted from nature are also polymorphic, with 16% of the Ys lacking the Y-specific rDNA marker. The absence of this marker is significantly associated with the expression of aa in males. Hence, all three of the major genetic determinants of the abnormal abdomen syndrome are polymorphic in this natural population.

Abdomen↗
PubMed1975

Role of DNA sequences in genetic recombination in the iso-1-cytochrome c gene of yeast. I. Discrepancies between physical distances and genetic distances determined by five mapping procedures.

Recombination rates have been examined in two-point crosses of various defined cyc1 mutants using five mapping methods. Nucleotide sequences of mutant codons were identified in previous studies from alterations in functional iso-1-cytochromes c produced by intragenic revertants. Heteroallelic diploids were analyzed for rates of mitotic recombination that occurred spontaneously and that were induced with x-rays, ultraviolet light and the near-ultraviolet light emitted by sunlamps, as well as rates of meiotic recombination that occur after sporulation. Frequencies of both mitotic and meiotic recombination do not necessarily correspond with physical distances separating altered nucleotides. The most extreme discrepancy involved two adjacent intervals of thirteen basepairs which differed approximately thirty-fold in their spontaneous and X-ray-induced recombination rates. Marked disproportions between genetic and physical distances appear to be due to the interaction of the two nucleotide sequences in the heteroallelic combination and not to the sequences of the mutant codons alone. Recombination values that were obtained by all five methods could not be used to establish to correct order of mutant sitesmrelationships of the recombination rates for the various pairwise crosses are different after mitosis from those after meiosis, suggesting that these two recombinational processes are to some extent different in their dependence on particular nucleotide configurations. On the other hand, the relationships of the rates induced by UV-, sunlamp- and X-irradiation were identical or very similar. In addition to the intrinsic properties of the alleles affecting frequencies of mitotic and meiotic recombination rates, two- to threefold variations in recombination rates could be attributed to genetic backgrounds.

Base Sequence↗
PubMed2025

Noninvasive preimplantation genetic testing for aneuploidy using blastocyst spent culture medium may serve as a backup of trophectoderm biopsy in conventional preimplantation genetic testing.

BACKGROUND: To investigate whether the noninvasive preimplantation genetic testing (niPGT) complement conventional preimplantation genetic testing (PGT) in the embryos for aneuploidy. RESULTS: 40 spent culture medium (SCM) samples from routine embryo culture were collected, and half of each SCM (10 µL) sample was used for whole genome amplification, while the other half was stored at -80 °C for 3-6 months. Thirty-six out of 40 fresh SCM samples were successfully amplified and sequenced. Thirty-six paired frozen-thawed SCM samples showed 100% concordance with the freshly amplified SCM samples. Then, SCM and trophectoderm (TE) samples from 149 blastocysts from 51 couples were collected. A 98.0% successful SCM sample amplification rate (146/149) was achieved. For the 146 paired TE biopsy and SCM samples, the overall concordance rate was 82.9% (121/146). Ten embryos with aneuploid TE results but euploid niPGT results were donated. A 70.0% (7/10) true negative rate was achieved by niPGT with respect to the inner cell mass (ICM) results (TE-positive embryos). CONCLUSIONS: These results suggested that SCM stored at -80 °C for 6 months without affecting niPGT results based on NICSInst amplification.

Humans↗
PubMed1992

The load of genetic and partially genetic disease in man. IV. Severe visual handicaps and profound childhood deafness in Hungarian school-age children.

In Hungary, the school-age prevalences of severe visual handicaps and of profound childhood deafness have been estimated to be about 6/10(4) and 10/10(4), respectively. Most of these conditions have onset at birth or in early childhood and are aetiologically heterogeneous. Severe visual handicaps are grouped under 11 aetiological categories, their relative contributions to the prevalence being: perinatal damage syndrome (20%; half of this is due to retinopathy of premature infants), cataracts (15%), choroidoretinal degenerations (15%), congenital abnormalities of the eye (15%), syndromes (10%), high myopia +/- retinal detachment (7%), postnatal causes (5%), nystagmus (5%), optic atrophy (4%), bilateral retinoblastoma (2%) and prenatal causes (2%). Overall, Mendelian conditions (included under many of the above) account for about 50% with relatively more autosomal dominant than autosomal recessive and sex-linked entities, and acquired causes account for about 40% of the cases studied. No aetiology could be assigned in 10% of the cases. For profound childhood deafness, the rank order of the aetiological categories is: autosomal recessive entities (34%), postnatal causes (22%), perinatal causes (19%), autosomal dominant entities (17%), prenatal causes (5%) and unknown causes (3%). Severe childhood visual handicaps are responsible for about 60 years of loss of life per 10(4) live births and about 400 years of impaired life per 10(4) live births. Genetic causes account for one-quarter of lost life years and three-quarters of impaired life years. The comparable estimates for profound childhood deafness are: about 240 years of life loss per 10(4) live births (again, about one-quarter due to genetic causes) and about 640 years of impaired life per 10(4) live births (about one-half due to genetic causes). In all these calculations, it has been assumed that the average life expectancy at birth for an individual in the population is 70 years.

Adolescent↗
PubMed2025

Leveraging local ancestry and cross-ancestry genetic architecture to improve genetic prediction of complex traits in admixed populations.

The broader application of polygenic risk score (PRS) is hindered by the limited transferability of PRS developed in Europeans to non-European populations. While many statistical methods have been developed to improve the performance of PRS in non-European populations, most of them focused on discrete genetic ancestry clusters and did not consider admixed individuals. Admixed individuals pose a unique challenge for PRS calculation due to the complexity of local ancestry and cross-ancestry effect sizes. Here, we present a statistical method called SDPR_admix for calculating PRS in admixed individuals. SDPR_admix characterizes the joint distribution of the effect sizes of a genetic variant with two ancestries to be both zero, ancestry enriched, or shared with correlation. SDPR_admix outperformed other methods in simulations and improved the prediction of real traits in European-African admixed individuals in UK Biobank when trained on the Population Architecture using Genomics and Epidemiology (PAGE) dataset (N = 13,000). Deployment of SDPR_admix on All of Us (N = 52,000) further increased the prediction accuracy by approximately 5-fold on average compared with training on PAGE. This enhancement was achieved with manageable computational time and cost, demonstrating the feasibility of training PRS models on large-scale All of Us data. We provided several examples demonstrating that both ancestral-enriched and shared effects, as included in the SDPR_admix prediction model, are helpful for improving polygenic prediction in admixed populations. We also applied SDPR_admix to construct PRS for admixed Americans with mixture of European and Amerindigenous ancestries and showed that SDPR_admix overall outperformed other methods.

Humans↗
PubMedDate not supplied

Genetic analysis of cystic fibrosis in Denmark. Implications for genetic counselling, carrier diagnosis and prenatal diagnosis.

Cystic fibrosis is the most common, severe, inherited disease in the Caucasian population. As a consequence, the demand for genetic counselling of patients with cystic fibrosis and their families is large. In Denmark the incidence of cystic fibrosis is 1:4700, which is quite low compared to other European countries. We have investigated 268 Danish cystic fibrosis patients with respect to DNA markers (haplotypes) and the most common mutation delta F508. The delta F508 mutation is found on 88% of all cystic fibrosis chromosomes, the highest frequency reported so far. This had had an important impact on genetic counselling, prenatal diagnosis and eventually population screening. In the Danish population 78% of all couples at risk will be informative for delta F508 and will be identifiable by simple screening methods.

Cystic Fibrosis↗
PubMed1976

On the genetics and population genetics of Gm(4).

Investigations on 70 German families with 142 children confirmed the autosomal-dominant inheritance of Gm(4). However, in our material as well as in the materials published so far, Gm(4) X Gm(-4) parental combinations show clear surplusses of Gm(4) and deficits of Gm(-4) children, which might indicate prenatal selection. The world distribution of Gm4 alleles reveals a remarkable racial heterogeneity. Furthermore, marked North-South distribution gradients in Caucasoids and Mongoloids were found. The genetical and population genetical observations are discussed.

Adult↗
PubMed1977

[Medico-genetic study of the population of the Samarkand region. II. Population-genetic description of 4 kishlaks of the Urgut district].

This report is a second one in a series of works devoted to the medico-genetical screening of Uzbekistan populations. The paper comprises the results of the analysis of the populational structure of one of the village councils (soviets) of the Urgut District of the Samarkand Region. The main parameters of the population studied were as follows: total number 1529 persons, the average number of inhabitants of one village--328. The proportion of the inhabitants studied--56%, the average number of persons per family--5.22; the average period between subsequent generations--30-35 years, the gametic index--0.8, the inbreeding coefficient inferred from pedigrees--0.018899--0.00781, Fst = 0.03577, the average genetic distanse according to Edwards--0.0231-0.0671. The distribution of Mendelian markers (ABO, Rh, Hp and Ptc) was studied. The observed ratio between a high degree of inbreeding and a relatively low extent of isolation of populations permits to explain satisfactorily the distribution and frequencies of hereditary pathology in the Urgut District of the Samarkand Region pointed out in the previous report.

Adolescent↗
PubMed1978

[Medico-genetic study of the population of Uzbekistan. IV. Medico-genetic description of the population of 4 villages of the Urgut district of the Samarkand region].

The data about the incidence of hereditary diseases and those with genetic predispositions which received after subtotal medico-genetical examination of the inhabitants of 4 villages in the Urgut district of the Samarkand province are presented. 848 inhabitants (348 adults and 464 children aged 7--16 years) are examined. The nosological profile of the morbidity and spectrum of the Mendelian diseases in the population is evaluated. The integrative estimate of load of the detrimental (non-lethal) genes is about 0.166 per individual.

Adult↗
PubMed1978

Genetic control of the immune response to the H-2Dk private specificity, H-2.32. II. Genetic linkage analysis of a backcross generation.

B10.AKM mice (H-2M) when immunized with H-2k cells showed very low cytotoxic antibody responses to the H-2Dk private specificity H-2.32, whereas AKR.M and (AKR.M X B10.AKM)F1 mice that possess the same H-2m haplotype mounted reasonable anti-H-2.32 antibody responses. The genetic nature of the non-H-2 linked gene(s) controlling the anti-H-2.32 response was analyzed on the backcross progeny raised between (AKR.M X B10.AKM)F1 and B10.AKM mice. The anti-H-2.32 antibody response was found to be predominantly controlled by a single locus. This locus segregated independently of the Ig heavy chain locus, the Ly2 locus, and the Mls locus. Despite the observed difference in antibody production, no significant differences between AKR.M and B10.AKM mice were detected in induction of H-2Dk-specific killer T cells. Thus, the defect in the response of B10.AKM mice to H-2.32 can be detected at the level of B cell function and is controlled by a single non-H-2-linked genetic locus, but is not attributable to genes linked to the major immunoglobulin structural genes nor to the Mls locus.

Animals↗
PubMed1979

Genetic properties of the Salmonella enteritidis R404 plasmid aggregate. IV. Reconstruction in R404 plasmid aggregate and separation of twelve genetically distinct derivative forms.

R404 plasmid aggregate is composed of two conjugative and two nonconjugative plasmids. Plasmid aggregate reconstructed from separated plasmids had the same genetic properties as the original R404 plasmid aggregate. It was found that plasmids of R404 factor could be transferred in conjugation in twelve different sets. These twelve genetically distinct classes of transconjugants formed only six groups differing in phenotypic characters.

Conjugation, Genetic↗
PubMed1979

Population genetics of Drosophila amylase. I. Genetic control of tissue-specific expression in D. pseudoobscura.

Drosophila pseudoobscura is polymorphic for tissue-specific expression of alpha-amylase in adult midguts. This enzyme is encoded by a single locus, Amy, on the third chromosome. In this paper we show: (1) Up to about 12 days post-eclosion, the midgut activity patterns remain stable; after 12 days areas not showing activity previously begin to show activity. Thus, the genes controlling the expression of Amy are temporally acting. (2) Diet affects the quantitative, but not the qualitative, expression of Amy. (3) The expression of Amy in adult midguts is under genetic control. Selection for different frequencies of patterns is possible; realized heritabilities are 0.20 to 0.50. Partial linkage with third chromosome inversions has been demonstrated; the genes or elements controlling Amy expression are not, however, confined to the third chromosome. (4) The genetic elements controlling tissue-specific expression of amylase do not coordinately control the expression of five other "digestive-type" enzymes that were studied.--This polymorphism appears to be analogous to that studied by Abraham and Doane (1978) in D. melanogaster, wherein they have mapped regulatory genes.

Amylases↗
PubMed1978

Genetic counselling and genetics of cleft lip and cleft palate.

Modern neonatal care and advanced plastic surgical correction have led to the survival of most newborns with oral clefts. These children are likely to reproduce. A slight increase in the incidence of oral clefts may be expected in the future. The genetics of cleft lip and cleft palate is reviewed. The inheritance is usually multifactorial. With normal parents the risk of having a first affected child with cleft lip is about one per thousand, the risk of having a second affected child 4 per cent and the risk of having a third affected child 10 per cent. If a parent has already a cleft lip, the risk of having a first affected child now is 4 per cent, while the risk of having a second affected child is 10 per cent. The methodology of genetic counseling is given.

Abnormalities, Drug-Induced↗
PubMed1978

Genetic fate of DNA in a strain of Bacillus subtilis which is impaired in genetic transformation.

A mutation in Bacillus subtilis call recC4 which results in an impairment of genetic transformation was transferred to a new strain using the closely linked marker mit-2 (mitomycin C-resistance) for selection. This derived strain was in turn impaired in transformation but showed normal levels of sensitivity to ultraviolet irradiation and methyl methane sulfonate. The genetic and molecular fate of transforming DNA in the recC4 strain was studied. Normal amounts of DNA were taken up by the cells and this DNA or parts of it became associated with recipient DNA. Linkage between genes on donor and recipient molecules was, however, not established and transformants were not generated. The recC4 mutation therefore affects a step in the recombination pathway during transformation. Either the association between donor and recipient DNA molecules is abnormal or the cells are deficient in the further processing of the associated complex.

Bacillus subtilis↗
PubMed1975

Genetics of acheiropodia (the handless and footless families of Brazil). IX. Genetic counseling.

Acheiropodia offers no special problem of a counseling nature. The genetic risk can be easily estimated since the anomaly is due to a rare autosomal recessive gene with complete penetrance and little variation in expression. However, considering that acheiropod individuals have a tremendous handicap (they are born without both hands and feet), it is remarkable how they overcome this difficulty and lead an almost 'normal' life. Several examples are given in this paper. The 'philosophy' of genetic counseling is briefly discussed; emphasis is placed upon the necessity for the geneticist to present the good perspectives, while preparing the consultand for the worst. Even in this last possibility, however, not everything is necessarily lost as the example of the acheiropods attests.

Abnormalities, Multiple↗
PubMed1977

Genetic and non-genetic effects on plasma LH concentrations in lambs at 4 and 8 weeks of age.

Plasma LH was measured at 4 and 8 weeks of age in purebred lambs born to Finnish Landrace, Galway, Fingalway and High Fertility ewes. The average litter sizes for these breeds vary from 1.4 to 2.5. Lambs born after the transfer of fertilized eggs (all Fingalway) to Finnish Landrace, Galway and Fingalway ewes were also studied. There was evidence for a significant positive effect of selection for litter size within the Galway breed on plasma LH at 8 weeks of age. Finnish Landrace lambs had significantly higher levels of plasma LH at 8 weeks of age than did Galway Control lambs. These two groups did not differ with respect to plasma LH at 4 weeks of age. Non-additive genetic effects were significant at 4 weeks of age. The ranking of genetic groups on plasma LH was not consistent with their ranking for litter size. There was no evidence for a maternal effect associated with breed of dam on plasma LH and the effects of litter size were generally insignificant. Female lambs had significantly higher levels of LH at 4 weeks of age but there was no sex difference at 8 weeks because LH levels in males had increased. The correlation between the level of plasma LH at 4 and 8 weeks of age was -0.04. It is concluded that plasma LH is unlikely to prove a practical aid to selection for increased fecundity in sheep.

Aging↗