A long interspersed (LINE) DNA exhibiting polymorphic patterns in human genomes

Genome scanning by two-dimensional DNA typing: the use of repetitive DNA sequences for rapid mapping of genetic traits

The existence of repetitive DNA sequences offers the possibility to assess the mammalian genome for individual variation in its entirety rather than at one or only a few sites. In order to fully explore the various sets of mammalian repeat sequences for this purpose, analytical tools are required which allow many if not all individual members of sets of repetitive elements to be resolved and identified in terms of location and allelic variation. We have applied and further developed an electrophoretic system, two-dimensional DNA typing, which may fulfill these requirements. The two-dimensional system combines separation of DNA fragments by size in a neutral gel, with separation by sequence composition in a denaturing gradient gel. By hybridization with minisatellite- and simple-sequence core probes and by inter-repeat polymerase chain reaction techniques, it is possible to obtain individual--and even chromosome-specific separation patterns that consist of hundreds of spots. Computerized image analysis and matching of such spot patterns allows the rapid assessment of multiple polymorphisms, spread over the genome, to monitor genetic variability in populations. When coupled to databases of polymorphic DNA markers with a known genomic location, two-dimensional DNA typing can greatly accelerate the mapping of genetic traits in humans, animals, and plants.

Enzymatic production of single-stranded DNA as a target for fluorescence in situ hybridization

This study demonstrates that Exonuclease III (Exo III) can be used to produce sufficient single-stranded (ss)DNA in chromosomes and cells to allow in situ hybridization. In this study, all of the probes were modified with biotin and the probe binding was visualized with fluorescein-labeled avidin. Exo III digestion starting at naturally occurring breaks in methanol-acetic acid preparations produced enough ssDNA for strong hybridization when human genomic DNA was used to probe human chromosomes. Pretreatment with the endonucleases EcoRI, Hind III and BamHI was used to produce more sites for initiation of Exo III digestion when using a chromosome-specific repetitive probe specific to a small chromosomal subregion near the telomere of human chromosome 1(1p36). The fluorescence intensity following hybridization to Exo III-treated targets was roughly equal to that following hybridization to thermally denatured targets, but background fluorescence was lower.

Mutation and psychosis: a suggested explanation of seasonality of birth

The persistence of psychosis at a high and relatively constant prevalence in the various populations of the world is rendered difficult to explain by the absence of identified environmental precipitants and by reduced fertility of affected individuals. The problem is not confined to schizophrenia but applies also to affective disorder. The 'virogene' concept attempts to explain this paradox as follows. (1) Psychosis in general is, as suggested by Böök (1953) and Lewis (1958) for schizophrenia, associated with a high rate of mutation. (2) The new mutations occur at a specific site (a 'hot-spot') in the genome and consist of rearrangements (e.g. transpositions or new insertions occurring as a result of unequal recombination) in a sequence which has a degree of potential autonomy, i.e. an integrated pathogen or 'virogene'. (3) The mutations occur specifically in the courses of gametogenesis in the male. By its location in the scrotal sac and its extended time course, gametogenesis in the male is susceptible to insertional mutagenesis as a function of variations in environmental temperature. Such temperature-dependent mutations are reflected in the seasonality of birth seen in both schizophrenic and affective illnesses. The increased likelihood of such mutations occurring with time is held to account for the association of psychosis with increased paternal age. (4) Such new events are held responsible not only for 'sporadic' cases in individuals without a family history of psychosis, but also for increases in severity of illness between generations. Psychosis is viewed as a continuum extending from unipolar through bipolar affective disorder and schizoaffective illness to schizophrenia with increasing degrees of defect.(ABSTRACT TRUNCATED AT 250 WORDS)