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Genetic analysis of several hundred progeny from crosses of two heterothallic species of Achlya and Dictyuchus provides preliminary information about the life cycle and pattern of sexuality in the biflagellate Phycomycetes. Extensive testing of mycelial progeny indicates a diploid life cycle. Control of sexual expression and mating competence appears to be based on a complex genetic system.
The genetic and environmental bases for differences in rate of development were investigated in 2 inbred strains of mice: C57BL/6By (B) and BALB/cBy (C). Twelve motor responses, aside from individual weight, were used to measure these differences. The Recombinant Inbred Strains method was chosen to perform the genetic analysis. Overdominance is shown to be present in 2 variables alone (eye opening, weight at 10 and 20 days). In most cases, each of the response reflexes was found to be associated with several genes (locomotion, hind limb, crossed extensor, righting, vibrissae placing, bar holding). Differences across strains are associated with one segregating unit for rate of disappearance of the rooting response. This unit is mapped on the part of the 4th chromosome including the loci b and H-21. The strain distribution pattern differs for each sensory motor response, consequently no one general genetic factor of development can be advanced. Maternal effects were found for 4 variables (grasping, fore limb placing, eye opening and weight). For two responses, the F1 pups developing the fastest were reared by mothers from the slowest developing parental strain. As regards this latter finding, the authors hypothesize that mothers differ as to the quality of the environment they furnish to their young and pups differ in their ability to benefit from these environments.
A genetic analysis is presented of data from 22 Brazilian sibships with cases of acheiropodia (the handless and footless families of Brazil). Segregation analysis performed using a 16K CDC 3100 computer showed a segregation frequency of .245 +/- .040, which is close to the expected value of .25. No sporadic cases were detected. The ascertainment of the probands was through multiple incomplete selection (pi = .55 +/- .07). The data are consistent with the hypothesis of an extremely rare autosomal recessive gene as the etiological factor in acheiropodia. Prevalence is estimated as 29 +/- 4, which is the same as the number of high risk cases; gene frequency equals .0009 +/- .0005, and the incidence at birth is 4 times 10(-6) by the indirect method or 7 times 10(-6) by the direct method. The frequency of heterozygotes at birth is assumed to be 0.18% (450 times the frequency of affected). Population size is approximately 10 million, and the number of founders on a unique-mutation hypothesis is estimated as about 500. All these estimates are first approximations and must be accepted with caution.
Fifteen behavioral measurements were taken on paradise fish of two inbred progenitor strains and of 16 recombinant lines derived from their cross and maintained under inbreeding with gynogenesis and sib-mating. Univariate and multivariate analyses showed significant differences among the RI means on all measures. Four combined variables extracted by principal component analysis showed that there were common sources of a large part of the behavioral variability measured in the arbitrarily designed test situations. There were no separate subgroups of the RI strain means, and overlapping ranges point to a polygenic genetic determination of the studied behavioral phenotypes. A biometrical analysis of the distribution pattern of recombinant lines and the progenitor strains showed that in several characters non-allelic genic interactions made a significant contribution to the variation. Additive and interaction components of the mean, the heritabilities and the minimum number of effective factors were estimated for all studied behavioral phenotypes, and the combined variables as well.
Cloning techniques make it possible to accommodate bacterial genes on vector DNA molecules. On that basis the investigation of bacterial structures and functions got new impetus. The potentials of molecular genetics for detailed analysis of bacterial structures are illustrated in this paper for the gene cluster involved in the expression of F72 fimbriae associated with a uropathogenic Escherichia coli O6:K2:H1:F7 strain.
In Drosophila melanogster females the segregation of nonexchange chromosomes is ensured by the distributive segregation system. The mutation noda specifically impairs distributive disjunction and induces nonexchange chromosomes to undergo nondisjunction, as well as both meiotic and mitotic chromosome loss. We report here the isolation of seven recessive X-linked mutations that are allelic to noda. As homozygotes, all of these mutations exhibit a phenotype that is similar to that exhibited by noda homozygotes. We have also used these mutations to demonstrate that nod mutations induce nonexchange chromosomes to nondisjoin at meiosis II. Our data demonstrate that the effects of noda on meiotic chromosome behavior are a general property of mutations at the nod locus. Several of these mutations exhibit identical phenotypes as homozygotes and as heterozygotes with a deficiency for the nod locus; these likely correspond to complete loss-of-function or null alleles. None of these mutations causes lethality, decreases the frequency of exchange, or impairs the disjunction of exchange chromosomes in females. Thus, either the nod locus defines a function that is specific to distributive segregation or exchange can fully compensate for the absence of the nod+ function.
Variation in the chromosomal genomes of 1527 isolates of eight common serotypes (O and H antigen profiles) of Salmonella was assessed by analysis of electrophoretically demonstrable allelic polymorphism at 23 metabolic enzyme loci. Seventy-one distinctive electrophoretic types, representing multilocus genotypes, were identified. A basically clonal population structure was indicated by the presence of strong linkage disequilibrium among enzyme loci, the association of each serotype with a relatively small number of multilocus enzyme genotypes, and the global distribution of certain genotypes. For each of six of the serotypes, 83-96% of isolates were members of a single clone. The occurrence of each of four serotypes (S. derby, S. enteritidis, S. infantis, and S. newport) in isolates of clones belonging to several evolutionary lineages, some of which are distantly related, suggests that the horizontal transfer and recombination of chromosomal genes mediating expression of cell-surface antigens has been a significant process in the evolution of the salmonellae. Two divergent clone clusters of S. derby differ in the relative frequency with which they cause disease in birds versus mammals, and two major lineages of S. newport differ in the frequency with which their clones are associated with disease in humans versus animals.
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A biometrical-genetical analysis of twin data to elucidate the determinants of variation in extraversion and its components, sociability and impulsiveness, revealed that both genetical and environmental factors contributed to variation in extraversion, to the variation and covariation of its component scales, and to the interaction between subjects and scales. A large environmental correlation between the scales suggested that environmental factors may predominate in determining the unitary nature of extraversion. The interaction between subjects and scales depended more on genetical factors, which suggests that the dual nature of extraversion has a strong genetical basis. A model assuming random mating, additive gene action, and specific environmental effects adequately describes the observed variation and covariation of sociability and impulsiveness. Possible evolutionary implications are discussed.
Cancer is genetic, in the sense that it is caused by DNA alterations at the cellular level. On the other hand, the most important risk factors for the common cancers are environmental: cigarette smoking, environmental pollution, occupational exposures, poor diet, and so on. These two observations are not in conflict: the DNA alterations that lead to cancer are very likely to be caused by environmental mutagens. It would be valuable to know exactly what genes are altered to cause a specific cancer, because the effects of these alterations might then be reversible before cancer has a chance to develop. A key to identifying these cancer genes may lie with rare families at extremely high risk of a specific cancer. Unlike most cancer patients, members of these families may inherit an alteration that confers increased susceptibility to cancer. In these rare instances, cancer is a genetic disease at the level of the family, as well as at the level of the cell. Therefore, in these families, genes predisposing to cancer can be mapped in the same way as genes for purely genetic diseases like sickle cell anaemia, cystic fibrosis, and Huntington's disease. The hypothesis that underlies the mapping of cancer genes in families is that the genes inherited in altered form in these rare families are the same genes that are altered in somatic cells of individuals without a remarkable family history of cancer. This hypothesis has proved correct for retinoblastoma. Genes responsible for other rare cancers have been mapped in families as well: neurofibromatosis, multiple endocrine neoplasia, Wilms' tumour, and colon cancer following familial adenomatous polyps, among others. Genes responsible for common cancers are also being defined by genetic analysis, most notably breast cancer and colon cancer. This review summarizes why, how, and what genetic analysis of families can reveal about human cancers.
We report a developmental and genetic analysis of the X-linked vital locus l(1)EC7 in Drosophila melanogaster. The locus maps in the salivary band region 1B4-5 to 1B8-9, a part of the X chromosome previously shown to be essential for normal neural development. Certain mutant alleles at the locus can cause embryonic lethality, indicating that the function provided by the gene is essential during embryogenesis. A developmental analysis of gynandromorphic genetic mosaics shows that: (1) the gene function is autonomously essential in the eye; (2) the gene function is essential for normal development of the optic lobes; and (3) the gene function is not necessary in most major imaginal-disc cell derivatives with the exception of the eye disc. Conclusions from the developmental analysis of a temperature sensitive allele are consistent with those from the mosaic analysis. The embryonic lethality caused by the mutant alleles and abnormalities observed in the genetic mosaics have led us to rename the locus l(1)EC7 to elav (embryonic lethal, abnormal visual system).
A clinical genetic examination of 22 cases of hereditary microcephaly in 11 families was carried out. Parent consanguinity (first and second cousins) was ascertained in 7 families. Genetic analysis of the experimental material performed by Weinberg's method showed significantly recessive course of the genuine microcephaly inheritance. High frequency of low degree mental retardation (30%) among probable recessive genes carriers of microcephaly (of the parents and their siblings) was ascertained and that confirmed the possibility of gene heterozygous state manifestation. The gene frequency fluctuated from 0,0042 to 0,024. About 3500 people might show low forms of mental retardation in connection with probable non-penetration (about 30%) of the microcephaly genes being in heterozygols state.
As a result of crosses between the SHR rats (spontaneously hypertensive strain) and WKY rats (normotensive strain), the F1 and F2 hybrids and the B1 and B2 backcrosses were obtained. Analysis of genetic control nature in these generations revealed that the WKY genes responsible for the level of arterial pressure, sensitivity to the electric current stimulation and salt (sodium and potassium) appetite characteristics were dominant. The heterosis effect was found for the body mass. Analysis of dynamics of different types of exploratory activity (in a shuttle box, in "horizontal plane", in an open field) demonstrated specificity of their genetic formulae and peculiarities of changes in their genetic control during the test.
Automation of several new, non-traditional techniques for genetic analysis has now become possible. A new system is described that performs gel electrophoretic analysis of DNA including VNTRs, gene segments, and restriction enzyme digests. The instrument detects emitted fluorescence from labeled DNA segments in real-time as they electrophore through a gel matrix past a scanning laser beam. Molecular length determination and band quantification is accomplished by comparison to an in-lane standard. Since DNA segments can be labeled and detected with any of four different dyes, the simultaneous analysis of similar length segments from different reactions within a single lane is possible. PCR products are analyzed for research in the areas of human identification and genetic disease. These examples illustrate how automation will play key role in this new era of genetic analysis.
Bacteria of the genus Vibrio are remarkably diverse, and until recently the methodology for genetic analysis consisted of a patchwork of different approaches, many of which were narrowly applicable to a single species. The invention of the recombinant DNA technology and the subsequent innovations in transposon mutagenesis and in transductive and conjugative gene transfer techniques have led to the development of very powerful and general strategies for genetic analysis of species of Vibrio. The striking synergy of combining recombinant DNA, transposon, and gene transfer methods is particularly evident in the construction of transposons which generate gene fusions and of broad host range plasmids which deliver transposons and mutated genes and which mobilize chromosomes. With such tools it should be possible to perform advanced genetic analysis on the many undomesticated species of Vibrio still to be explored.
In a collaborative effort by 12 centers from Europe and North America, data were assembled from 94 multiplex families with insulin-dependent diabetes mellitus (IDDM) for analysis of genetic and other factors of possible etiological importance. The dataset contains information on the following genetic markers: HLA-DR beta and -DQ beta restriction fragment length polymorphisms (RFLPs), three RFLPs detected with two probes that map 5' to the insulin gene, the serologically defined HLA loci, and the immunoglobulin allotypes. Data also were included for auto-antibodies to insulin and pancreatic islet cells as possible indicators of pathogenesis and for antibodies to certain viruses that have been implicated as "triggering" agents in IDDM. Medical history of family members was obtained by means of a uniform questionnaire. Identical copies of the dataset were distributed to anyone wishing to participate in the analysis for the IDDM component of GAW5. The multiplex IDDM family dataset is now available on request for further analysis.
As a result of recombination experiments between auxotrophic mutants of S. erythreus BTCC2 haploid recombinants and heteroclones were isolated. A genetic map of S. erythreus, including 15 auxotrophic loci was constructed by genetic analysis of the segregants of the heteroclones obtained. The genetic distances between 7 key loci on the map were determined and the entire length of the map of about 105 standard recombination units was calculated.
By selecting for mutations which could rescue the meiotic lethality of a rad52 spo13 strain, we isolated several new Rec genes required relatively early in the meiotic recombination process. This paper presents data to confirm that two of them, REC102 and REC107, are general, meiosis-specific recombination genes that have no detectable role during mitosis. Sequence analysis and genetic complementation indicate that REC107 is identical to the MER2 gene. No sequences related to REC102 have been found in the GenBank or EMBL collections. REC102 is expressed only in meiosis, prior to the reductional division, at about the time that genetic recombination occurs. Examination of the REC102 sequence indicates the presence of several sequences which may play a role in the regulation of its expression; however, the URS1 sequence commonly found in genes expressed early in meiosis is not present.