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At least 19 recordsLinked to original sources
PubMed1977

Analysis of family history data for evidence of non-Mendelian inheritance resulting from vertical transmission.

A number of infections of man, as well as of other animal and plant species, are heavily dependent upon 'vertical transmission'--that is direct parent-to-progeny transfer--for their maintenance in host populations. Such vertical transmission may be considered as a form of inheritance. It is usually non-Mendelian. This paper discusses the implications of such inheritance for the distribution of disease in families. A method is described for making quantitative predictions of prevalence rates of infection and of disease within different classes of relatives of either infected or uninfected probands. It is pointed out that, whereas a maternal line excess is to be expected among relatives of positive probands, the opposite should be found in families of negative probands. Expected differences between maternal and paternal line prevalence rates of observable disease decline rapidly with distance of relationship from the proband, and are greatly reduced by diagnostic insensitivity (analogous to penetrance). The implications of this analytic method for the design of family history studies are discussed. Published data on familial breast cancer are reviewed, and found to show no evidence that this condition is associated with a non-integrated vertically transmitted agent.

Carrier State↗
PubMed1975

The non-Mendelian inheritance of Lewis-c blood group substance, as demonstrated in the case of a Bombay, Le(a-b-c-) saliva.

A Bombay, Le(a-b-) saliva was shown to lack Pneumococcus type XIV activity, an unusual situation, since this sample should be rich in this precursor to the ABO blood group substances. However, the sample was found to contain a new serological specificity, Le-c. It is argued that simple Mendelian inheritance does not occur with Le-c and single gene control cannot be demonstrated. Failure to repress a fetal gene at birth, as implicated by the similarity in structure between Le-c and carcinoembryonic antigen [SIMMONS and PERLMANN], has been excluded as the mechanism of inheritance of this blood group substance, due to the inability to detect carcinoembryonic antigen in the test saliva.

ABO Blood-Group System↗
PubMed2026

Digenic inheritance of mutations in SPG7 and AFG3L2 causes motor neuron and cerebellar disorders.

BACKGROUND: Biallelic SPG7 mutations cause one of the most common forms of hereditary spastic paraplegia (HSP). Several reports have suggested that heterozygous SPG7 variants may also play a role in HSP, but also in amyotrophic lateral sclerosis (ALS). However, it remains controversial whether heterozygous SPG7 mutations are pathogenic on their own, or if other mechanisms are at play. We recently provided evidence for non-Mendelian inheritance in spastic paraplegia 7 (SPG7), as heterozygous carriers of SPG7 mutations often also carried mutations in other disease-related genes, including AFG3L2, more frequently than expected by chance. Given that SPG7 and AFG3L2 encode interacting subunits of the mitochondrial m-AAA protease complex, we hypothesized that combined heterozygous mutations in these genes may act synergistically to disrupt mitochondrial function and contribute to disease. In this study, we aimed to examine whether digenic heterozygous mutations in SPG7 and AFG3L2 can lead to a spectrum of neurodegenerative disorders. METHODS: We first analyzed genome and exome sequencing data of 6644 unrelated individuals including 4817 motor neuron disorder (MND) and ataxia patients and 1827 controls. We next analyzed an additional 18,748 exome data from rare disease cohorts to further examine the occurrence of variants in SPG7 and AFG3L2. RESULTS: Among the first 4817 MND and ataxia patients, we identified a total of 6 patients, 4 of whom were unrelated, who carried potentially pathogenic variants in both SPG7 and AFG3L2, in contrast to none in 1827 unrelated controls. Further analysis of the 18,748 additional patients with rare disease, as well as a comprehensive literature review, identified 6 more patients, 5 of whom were unrelated, who had digenic mutations in SPG7 and AFG3L2. In the two families we identified, digenic mutations in SPG7 and AFG3L2 perfectly segregated with the disease. The 12 patients reported here exhibited predominant signs of motor neuron and cerebellar involvement. CONCLUSIONS: Our findings demonstrate that digenic inheritance of concurrent heterozygous mutations in SPG7 and AFG3L2 may cause motor neuron and cerebellar disorders. Screening of the entire SPG7 and AFG3L2 genes in genetically undiagnosed cases of MND and spastic ataxia may help to increase the diagnostic yield.

Humans↗
PubMed2026

Maize Gametophytic factor loci Ga3 through Ga11 modify reproductive barriers.

Gametophytic factor (Ga) barriers are maize (Zea mays ssp. mays) reproductive barriers controlled by molecular incompatibilities between pollen and silks. Twelve distinct Ga loci have been identified in maize populations since the first genetic evidence of a Ga barrier was reported in 1901. Of the twelve, however, only three have been validated by modern molecular, functional and genomic studies: Ga1, Ga2, and Tcb1. The remaining "higher" Ga loci, spanning Ga3 to Ga11, were reported in the historical literature, but their associated phenotypes segregated in unexpected ways or disappeared over subsequent generations. Here we introduce and explore the hypothesis that the higher Ga loci represent modifiers of Ga1, Ga2, and Tcb1 barrier functions. By revisiting the historical literature, we found that barrier phenotypes fall into two phenotypic and functional categories. Phenotypically, the two categories represented healthy pollen with a silk-length effect and unhealthy pollen without a silk-length effect. These phenotypic categories were supported by genomic data; we identified candidate genes in each higher Ga locus by comparing historical linkage mapping data to the corresponding genomic sequence of maize reference line B73. We discovered candidate genes related to two broad pathways: pollen tube growth and RNA-directed DNA methylation. We conclude that the past century of evidence aligns with our hypothesis that maize loci Ga3 through Ga11 modify rather than directly control Ga barriers. This brief investigation provides a starting point for geneticists and evolutionary biologists to explore how strong reproductive barriers are shaped by epistatic interactions.

Epistasis↗
PubMed1979

Altered chloroplast ribosomal proteins in a yellow mutant of Chlamydomonas reinhardii.

Ribosomes and ribosomal proteins from wild-type and a yellow mutant of Chlamydomonas reinhardii were analysed and compared by two-dimensional gel electrophoresis. Mixothrophycally grown yellow-27 mutant differs from wild-type cells in lowered chlorophyll content and grana formation of the chloroplast. Analytical ultracentrifuge analyses of cell extracts show a reduced amount of free 70S ribosomes and increased level of 50S subunits in the mutant cells. Similar results were obtained by electronmicroscopical method. Two-dimensional gel electrophoresis shows alterations in protein composition of 70S ribosomes of the mutant. Two proteins of 70S ribosomes have been altered. One of them with high molecular weight is practically absent while there is an additional, intensively stained spot in the mutant. Since the mutation is inherited in a non-Mendelian manner it is possible that the protein alterations in 70S ribosome are localized in the chloroplast DNA.

Chlamydomonas↗
PubMed1977

A comparison of small circular DNA molecules in psi+ and psi- strains of Saccharomyces cerevisiae.

The psi+ and psi- phenotypes, which affect the efficiency of ochre suppression in yeast, are inherited in a non-Mendelian fashion. There is no apparent difference in length or in length distribution of 2 micronm circular DNA molecules between psi+ and psi- strains. It seems that the psi genetic determinant is probably not connected with the presence or absence of these small circular DNA molecules.

DNA, Circular↗
PubMed1978

Abnormal mitochondrial genomes in yeast restored to respiratory competence.

When crosses are performed between newly arisen, spontaneous petite mutants of Saccharomyces cerevisiae, respiratory competent (restored) colonies can form. Some of the restored colonies are highly sectored and produce large numbers of petite mutants. The high-frequency petite formation trait is inherited in a non-Mendelian manner, and elimination of mitochondrial DNA from these strains results in the loss of the trait. These results indicate that abnormal mitochondrial genomes are sometimes formed during restoration of respiratory competence. It is hypothesized that these abnormalities result either from recombination between mitochondrial DNA fragments to produce molecules having partial duplications contained on inverted or transposed sequences, or else recombinational "hot spots" have been expanded.

DNA, Mitochondrial↗
PubMed1979

Yellow mutations alter chloroplast ribosomal proteins in Chlamydomonas reinhardii.

Ribosomes and ribosomal proteins from wild-type and three yellow mutants of Chlamydomonas reinhardii were analyzed and compared by two-dimensional gel-electrophoresis. Mixotrophycally grown mutants differ from wild-type cells in lowered chlorophyll content. Analytical ultracentrifugation analysis of cell extracts showed a reduced amount of 70S ribosomes and an increased level of 50S subunits in mutants y-27 and y-28. Two-dimensional gel electrophoresis indicated considerable alterations in the protein composition of 70S ribosomes of the mutants. Two proteins of 70S ribosomes were altered in the y-27 and y-28 mutants. Two proteins were absent from the electrophoretograms of the yellow-76 mutant and seven proteins were present in lowered concentrations. The mutations are inherited in a non-Mendelian manner. The protein alterations in 70S ribosome are most probably localized in the chloroplast DNA.

Chlamydomonas↗
PubMed1975

Isolation of a catabolite repression mutant of yeast as a revertant of a strain that is maltose negative in the respiratory-deficient state.

A character originating from Saccharomyces cerevisiae 1403-7A is described which interferes with maltose growth in the respiratory-deficient state. This character is inherited in an apparently non-Mendelian way, but at present no statement can be made concerning the localization of this character on a plasmid or the involvement of multiple genes. As a revertant of this character, a flaky mutant was isolated, showing a heavy flocculation during growth on liquid medium and resistance to catabolite repression for maltase, alpha-methyl-glucosidase, invertase, and succinate dehydrogenase. In wild-type cells, repression (caused by growth on 2% glucose) and derepression (caused by growth on 2% galactose) can be correlated with a lower and a higher level of cyclic 3',5'-adenosine monophosphate (cAMP), respectively. In cells of flaky mutant, growth on these carbon sources results in the same levels of cAMP as observed for the wild type. Consequently, in this mutant derepression in the presence of 2% glucose is not reflected in a higher level of cAMP.

Cell-Free System↗
PubMed1977

The mitochondrial genome of Chlamydomonas. II. Genetic analysis of non-mendelian obligate photautotrophic mutants.

Among a collection of obligate photoautotrophic (dark-dier, dk) mutants isolated in Chlamydomonas reinhardtii, two have been found which are inherited in crosses to wild type in a non-Mendelian, biparental and apparently random fashion. F1 progeny include not only cells which show the dk and wildtype parental phenotypes but also many which possess intermediate phenotypes between wild type and dk. When F1 progeny with dk, intermediate or wild-type phenotype were backcrossed to wild type, the dk phenotype continued to be inherited in a biparental and random fashion. Upon selection, neither mutant formed stable clones producing only dk progeny, suggesting that the two mutants segregate dk and wild-type progeny somatically and that the homozygous dk condition may be lethal. The biparental transmission of these two non-Mendelian dk mutations resembles the transmission of acriflavin-induced minute mutations of Chlamydomonas and is distinct from the uniparentally inherited chloroplast mutations of this alga. Both the dk and minute mutations may alter mitochondrial DNA and thereby alter mitochondrial functions.

Animals↗
PubMed1978

Non-Mendelian female sterility in Drosophila melanogaster: influence of ageing and thermic treatments. I. Evidence for a partly inheritable effect of these two factors.

Crosses between certain Drosophila melanogaster strains may give rise to female sterility of non-Mendelian determination. Reduced fertility is observed in F1 females, known as SF females, from crosses between females of "reactive" strains and males of "inducer" strains. The extent of this reduction of fertility depends on the strains which are used in the cross and on two non-genetic factors: age and temperature. The fertility of SF females increases with ageing. Also, exposing them for a short period to a high temperature (29 degrees C) either increases or decreases the probability of hatching of the eggs according to the stage of oogenesis at which the heat treatment is applied. A very striking point is that qualitatively quite similar, though attenuated, effects are observed when the two factors (ageing and temperature) are applied not directly to SF females, but to their maternal ancestors: mothers and grandmothers.

Aging↗
PubMed2025

Chromatin state dynamics of autosomes and the B chromosome during spermatogenesis in Pseudococcus viburni.

The mealybug Pseudococcus viburni is a plant-feeding insect with a non-Mendelian genetic system known as paternal genome elimination (PGE). In PGE, males eliminate their paternally inherited chromosomes during meiosis, transmitting only the maternal genome to the next generation. This involves genome-wide imprinting, where paternal chromosomes are heterochromatinised in embryogenesis and throughout adulthood. In this species, a non-essential B chromosome can escape paternal genome elimination, thereby enhancing its transmission rate to the next generation. Previous studies show that the B chromosome escapes elimination by changing its chromatin compaction during meiosis to resemble that of maternal chromosomes. Although the exact mechanism underlying this change is poorly understood. Here we investigated histone methylation and acetylation modifications, as well as the Heterochromatin Protein 1 (HP1), to characterise differences between maternal, paternal and B chromosomes during male meiosis of P. viburni. Maternal and paternal chromosomes show distinct histone modification patterns, with marks associated with euchromatin present on maternal chromosomes and marks associated with heterochromatin present on paternal chromosomes. We then identified key histone modification changes that coincide with chromatin remodelling of the B chromosome, which allows it to segregate with maternal chromosomes. In addition, we showed that these chromatin modifications occur regardless of the parental origin of the B chromosome. Overall, our findings support the role of histone modifications for proper chromosome segregation during meiosis in mealybugs and provide insight into the mechanisms by which the B chromosome exploits PGE for its preferential transmission.

Animals↗
PubMed1975

Assembly of the mitochondrial membrane system. Cytoplasmic mutants of Saccharomyces cerevisiae with lesions in enzymes of the respiratory chain and in the mitochondrial ATPase.

Mutants of Saccharomyces cervisiae with defects in enzymes of the electron transfer chain and in the rutamycin-sensitive ATPase have been isolated. Some of the mutants are specifically affected in either cytochrome oxidase, coenzyme QH2-cytochrome c reductase or ATPase. Other strains are deficient in both cytochrome oxidase and coenzyme QH2-cytochrome c reductase but still have rutamycin-sensitive ATPase. All the mutants reported in this study fail to be complemented by a rho0 tester derived from a respiratory competent strain. The meiotic spore progeny obtained by mating the mutants to a respiratory competent haploid yeast, when scored for growth on glycerol, show a non-Mendelian segregation of the phenotype. These two genetic tests indicate the mutations to be cytoplasmically inherited.

Adenosine Triphosphatases↗
PubMed1978

A comparative study of DNA-induced transformants and spontaneous revertants of inositolless Neurospora crassa.

Inositolless (inl-) Neurospora crassa strains were treated with DNA (allo-DNA) of wild type N. Crassa. Hyphal fragments of a mycelial suspension of the N. Crassa ragged inl- strain used as recipient in our transformation experiments were found to consist of units containing 100--1000 nuclei. In this strain the inositol-independent (inl+) nuclei appearing after DNA treatment or by spontaneous reversion are present in the cytoplasm together with a large number of inl- nuclei. Thus, both transformation and reversion initially must result in heterokaryosis. Under appropriate conditions the inl- nuclei can be detected in the transformed and spontaneous inl+ phenotype revertant strains. Spontaneous revertants are usually characterized by the loss of their inl+ nuclei after transfers on inositol-supplemented medium. On minimal medium, the growth rate of transformed strains is significantly lower than that of spontaneous revertants. The inl+ gene appearing after DNA treatment or by spontaneous reversion is inherited as a trait bound to chromosomes. In crosses with the transformed strains, there is a significant increase in the number of non-Mendelian (6:2 and 5:3) tetrads in the inl locus.

DNA, Fungal↗
PubMed1977

Mitochondrial heredity of resistance to 3-(3,4-dichlorophenyl)-1,1-dimethylurea, an inhibitor of cytochrome b oxidation, in Saccharomyces cerevisiae.

3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), an inhibitor of cytochrome b oxidation, has been used for the selection of three resistant mutants (diur) of Saccharomyces cerevisiae. The mutant diur-64 exhibits in vivo cross-resistance to antimycin A while diur-34 and diur-1 are more sensitive to antimycin A than the parental strain. The three mutants exhibit mitochondrial inheritance according to the following criteria: mitotic segregation of diuron-resistant and diuron-sensitive diploids is obtained among the diploid progeny of a cross between diur and dius; non-Mendelian segregation of diuron resistance (4:0) is observed in spores of tetrads issued from diuron-resistant diploid; extensive ethidium bromide treatment leads to the formation of Q- mutants which no longer transmit diur and dius alleles. Evidence for two distinct diuron-resistant loci were obtained by allelism tests. Recombination analysis shows that diuron-resistance is not located in the polar region of the mitochondrial genome. The diur loci are not linked to the erythromycin locus since the upper limit in recombinants frequency (26%) for a non-polar region is obtained between diur and eryr. A low recombinants frequency (3%) is observed in crosses between diur-34 mutation and the two mutants cob1 and cob2 suggesting that diur-34 might be located between these two cytochrome-b-deficient loci. The resistance to diuron is also expressed in vitro since the oxidation rates of succinate by sonicated submitochondrial particles from the mutants are clearly less sensitive to diuron than that of the wild type.

Antimycin A↗
PubMed1976

A cytoplasmic gene for partial suppression of a nuclear pleiotropic respiratory deficient mutant in the petite negative yeast Schizosaccharomyces pombe.

The nuclear pleiotropic respiratory-deficient mutant pet1 (previously M126) exhibits cytochromes aa3 and b deficiencies accompanied by loss of the oligomycin-sensitivity of the mitochondrial ATPase. The mutant pet1, unable to grow on glycerol, growth on glucose. The latter phenotypic trait symbolized by ANAS-D, exhibits a high frequency (2 to 4 X 10(5)) Of spontaneous suppression into Antimycin A-resistant strains. Mutagenesis with MnCl2 increases by a factor of 10(2) the frequency of ANAR-D derivatives. This suppression is partial since none of the suppressed strains is able to grow on glycerol even when respiratory functions and cytochromes activities are restored as in the pet1 [SUP2] strain. In the latter strain it is concluded that the extralocus suppressor gene [SUP2] is responsible for the ANAR-D trait. Tetrad analysis in a cross homozygous for pet1 demonstrates a non-Mendelian segregation pattern for the SUP2 suppressor gene. In stable diploids, homozygous for pet1, the [SUP2] suppressor exhibits a mitotic segregation pattern. Furthermore the transmission of the [SUP2] gene is decreased by ethidium bromide treatment. Therefore, the [SUP2] suppressor gene responsible for partial suppression of the nuclear pleiotropic phenotype in mutant pet1 is of cytoplasmic heredity.

Adenosine Triphosphatases↗
PubMed1975

Properties of cytoplasmic mutants of Saccharomyces cerevisiae with specific lesions in cytochrome oxidase.

Two mutants with specific defects in cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase; EC 1.9.3.1) have been isolated from cultures of Saccharomyces cerevisiae exposed to the mutagens ethyl-methane sulfonate and Mn++. The mutations have been shown to be extranuclear by two criteria. The phenotype persists in diploids formed by a cross with a p-o strain of yeast of the opposite mating type. Tetrad analysis indicates a non-Mendelian segregation (4:0 and 0:4) of the mutations. Both mutants show a total absence of cytochrome oxidase activity and of spectral cytochromes a and as. One of the mutants has been shown to be missing a polypeptide synthesized by mitochondria. The migration of this protein on polyacrylamide gels corresponds to the highest-molecular-weight subunit of cytochrome oxidase.

Diploidy↗