George Streisinger

Bio: George Streisinger is an academic researcher from University of Oregon. The author has contributed to research in topics: Zebrafish & Lysozyme. The author has an hindex of 28, co-authored 41 publications receiving 5282 citations. Previous affiliations of George Streisinger include Osaka University & California Institute of Technology.

Production of clones of homozygous diploid zebra fish ( Brachydanio rerio )

Abstract: Homozygous diploid zebra fish have been produced on a large scale by the application of simple physical treatments. Clones of homozygous fish have been produced from individual homozygotes. These clones and associated genetic methods will facilitate genetic analyses of this vertebrate.

Mechanisms of spontaneous and induced frameshift mutation in bacteriophage t4

Abstract: Frequencies of spontaneous and proflavine-induced frameshift mutations increased dramatically as a function of the number of reiterated base pairs at each of two sites in the lysozyme gene of bacteriophage T4. At each site, proflavine induces addition mutations more frequently than deletion mutations. We confirm that the steroidal diamine, irehdiamine A, induces frameshift addition mutations. At sites of reiterated bases, we propose that base pairing is misaligned adjacent to a gap. The misaligned configuration is stabilized by the stacking of mutagen molecules around the extrahelical base, forming a sandwich. Proflavine induces addition mutations efficiently at a site without any reiterated bases. Mutagenesis at such sites may be due to mutagen-induced stuttering of the replication complex.

Segregation analyses and gene-centromere distances in zebrafish

Abstract: The gol-1, gol-2, alb-1 and spa-1 mutations affect pigment pattern in the zebrafish. We show here that these loci are unlinked to each other. In addition, gene-centromere distances were determined for these loci by analysis of half-tetrads obtained by the inhibition of the second meiotic division. The fractions of tetratype (second-division segregation) tetrads range from 0.24 (spa-1) to 0.89 (gol-1). The observation of greater than 0.67 second-division segregation indicates that the zebrafish has high chiasma interference.

Chromosome structure in phage t4, iii. Terminal redundancy and length determination.

Abstract: In previous communications it was suggested that chromosomes of phage T4 are circularly permuted and terminally redundant.1 2 Heterozygotes formed by deletion ri mutants and r+, and by the host range alleles hI+ and h4±, were shown to behave as if they were due to this terminal redundancy.2 After infection and replication the chromosome of any one phage particle is assumed to become circularly permuted so that the genetic location of the beginning of any one progeny chromosome is randomly distributed over the genome. This could take place through the formation of recombinants by whole chromosomes or by fragments of chromosomes:

Stages of embryonic development of the zebrafish.

Abstract: We describe a series of stages for development of the embryo of the zebrafish, Danio (Brachydanio) rerio. We define seven broad periods of embryogenesis--the zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and hatching periods. These divisions highlight the changing spectrum of major developmental processes that occur during the first 3 days after fertilization, and we review some of what is known about morphogenesis and other significant events that occur during each of the periods. Stages subdivide the periods. Stages are named, not numbered as in most other series, providing for flexibility and continued evolution of the staging series as we learn more about development in this species. The stages, and their names, are based on morphological features, generally readily identified by examination of the live embryo with the dissecting stereomicroscope. The descriptions also fully utilize the optical transparancy of the live embryo, which provides for visibility of even very deep structures when the embryo is examined with the compound microscope and Nomarski interference contrast illumination. Photomicrographs and composite camera lucida line drawings characterize the stages pictorially. Other figures chart the development of distinctive characters used as staging aid signposts.

The zebrafish reference genome sequence and its relationship to the human genome.

Abstract: Zebrafish have become a popular organism for the study of vertebrate gene function. The virtually transparent embryos of this species, and the ability to accelerate genetic studies by gene knockdown or overexpression, have led to the widespread use of zebrafish in the detailed investigation of vertebrate gene function and increasingly, the study of human genetic disease. However, for effective modelling of human genetic disease it is important to understand the extent to which zebrafish genes and gene structures are related to orthologous human genes. To examine this, we generated a high-quality sequence assembly of the zebrafish genome, made up of an overlapping set of completely sequenced large-insert clones that were ordered and oriented using a high-resolution high-density meiotic map. Detailed automatic and manual annotation provides evidence of more than 26,000 protein-coding genes, the largest gene set of any vertebrate so far sequenced. Comparison to the human reference genome shows that approximately 70% of human genes have at least one obvious zebrafish orthologue. In addition, the high quality of this genome assembly provides a clearer understanding of key genomic features such as a unique repeat content, a scarcity of pseudogenes, an enrichment of zebrafish-specific genes on chromosome 4 and chromosomal regions that influence sex determination.

Intra-sexual selection in Drosophila.

Abstract: SINCE Darwin first wrote on the subject in 1871, sexual selection has been generally accepted as one of the basic facts of biology. The evidence in its favour seems, however, to be mainly circumstantial. Its existence has usually been inferred from sex differences depending on what are called secondary sexual characters which are supposed to have arisen as results of that selection. Such an approach has its dangers, and Huxley (1938) has made important criticisms of the original concept of sexual selection. He has shown that a large number of characters which have been attributed to sexual selection are unconnected with competition for mates. This is particularly the case in monogamous birds which offer some of the most striking examples of secondary sexual differences. In the first place monogamy, at least when the sexes are numerically equal, is the mating system least likely to develop sexual selection. In the second place, and more important, observations on bird behaviour have shown that much of the display of birds occurs after pairing, when competition must have ceased. Such sexual differences are concerned, either with inducing the female to copulate, or with maintaining the association of the sexes as long as it is necessary for the rearing of the young. Huxley therefore introduced the term epigamic to apply to characters which increased the fertility of a given mating and therefore had a selective value for the species as a whole. Epigamic selection includes the major part of what Darwin meant by sexual selection. It also includes selection for characters to which Darwin did not refer, such as the structure of copulatory organs, sex differences in frequency of crossing over, and the XY mechanism. It is only a special case of natural selection as generally understood. What remains of Darwinian sexual selection has been called intra-sexual selection, which denotes that it involves competition between members of one sex for mates. It can only indirectly affect the survival of the species and then is often deleterious (e.g. the cumbersome antlers of the stag). There is not invariably, however, a clear distinction between epigamic and intrasexual selection. In a promiscuous species like Drosophila pairing and copulation are synchronous. Courtship behaviour determines the number of mates and therefore enters into intra-sexual selection.

Ubiquitous somatic mutations in simple repeated sequences reveal a new mechanism for colonic carcinogenesis

Abstract: Spontaneous errors in DNA replication have been suggested to play a significant role in neoplastic transformation and to explain the chromosomal alterations seen in cancer cells. A defective replication factor could increase the mutation rate in clonal variants arising during tumour progression, but despite intensive efforts, increases in tumour cell mutation rates have not been unambiguously shown. Here we use an unbiased genomic fingerprinting technique to show that 12 per cent of colorectal carcinomas carry somatic deletions in poly(dA.dT) sequences and other simple repeats. We estimate that cells from these tumours can carry more than 100,000 such mutations. Only tumours with affected poly(dA.dT) sequences carry mutations in the other simple repeats examined, and such mutations can be found in all neoplastic regions of multiple tumours from the same patient, including adenomas. Tumours with these mutations show distinctive genotypic and phenotypic features. We conclude that these mutations reflect a previously undescribed form of carcinogenesis in the colon (predisposition to which may be inherited) mediated by a mutation in a DNA replication factor resulting in reduced fidelity for replication or repair (a 'mutator mutation').