Rapid determination of polyploidy in human chrorionic tissue sections

Summary Chromosomal analysis from aborted tissue has become an important diagnostic aid. However, the necessary cultures are frequently unsuccessful due to the condition of the aborted tissue. Polyploidy, in particular triploidy, in the conceptus is a common cause of early pregnancy loss and unlike aneuploidy does not appear to be associated with an increased recurrence risk. The necessity to monitor a subsequent pregnancy with amniocentesis is therefore eliminated. Therefore, in cases where a chromosomal anomaly is probable, a fast simple method of identification of a polyploid karyotype would be valuable. In this presentation, we describe a method using a scanning light microscope and histologic tissue preparations. This method can accurately determine the ploidy of the aborted material in 5 days.     

The linkage mapping of cloned restriction fragment length differences in Caenorabditis elegans

Summary The genomic DNA of two closely related strains of the nematode, Caenorhabditis elegans, Bristol (N2), and Bergerac (Bo), has different restriction endonuclease sites (Emmons et al. 1979). Since these two strains interbreed, it is possible to regard the restriction fragment length differences (RFLDs) as mutant variants. The N2 and Bo pattern can be segregated and mapped using clasical genetic techniques.Utilizing a number of genetic markers existing in the N2 strain, we have constructed hybrid populations homozygous for either Bristol or Bergerac over a given chromosomal region with random Bristol-Bergerac composition for the remainder of the genome. Genomic restriction digests from these hybrid populations were probed with random cloned fragments of Bristol DNA. In this way, fragments were mapped to genetically well characterized regions of the C. elegans genome. 27 probes which hybridize to a total of 310 Kb of DNA were found to exhibit six restriction fragment differences. Four of these differences have been mapped, providing probes for four different genomic regions. We have combined classical genetics and recombinant DNA technology to construct linkage maps of cloned DNA fragments using restriction fragment length differences. We are pursuing this approach in order to advance the knowledge of the genetic organization of C. elegans and to provide a means of cloning genes in an organism which provides an experimental model for the study of many biological systems. It is hoped that this approach will also provide a practical solution to some difficult problems in nematode strain identification. Furthermore, the characterization of the families of transposable elements responsible for generating many of the RFLDs will undoubtedly contribute to the understanding of the biological significance of these elements.     

The widespread declines of songbirds in rural Britain do not correlate with the spread of their avian predators

During the last 30 years, there have been marked declines in the populations of many British songbirds breeding on farmland, while two of their main predators, sparrowhawk (Accipiter nisus) and magpie (Pica pica), have spread back into areas from which they had disappeared. The causes of the songbird declines remain unclear but given the coincidence in timing, it might appear that increased predation could be responsible. Although many studies have failed to find links between changes in the populations of breeding songbirds and mortality from avian predators, previous work has, with few exceptions, involved only short-term studies on small spatial scales. Here we use large-scale, long-term data from a national bird census scheme to examine whether magpies and sparrowhawks could have depressed the rates of year-to-year population change in 23 songbird species. Our results indicate that magpies and sparrowhawks are unlikely to have caused the songbird declines because patterns of year-to-year population change did not differ between sites with and without these predators.     

Identification of a heat-shock pseudogene from Caenorhabditis elegans

While characterizing the hsp70 gene family from Caenorhabditis elegans we encountered an unusual member of this family. Sequence data reveal that the hsp-2ps gene is a pseudogene of the constitutively expressed, heat-inducible hsp-1 gene. Two stop codons generated near the 5' end of the sequence as well as several frameshift mutations and a large internal deletion confirm the identification of hsp-2ps as a pseudogene. The nucleotide substitution rate of the third codon position was twice that of the first and second codon positions, suggesting that the hsp-2ps gene was nonfunctional since the time of the duplication event. The hsp-2ps gene duplicates a region of the hsp-1 gene that lies exclusively within the transcribed region and retains the introns. We feel that the hsp-2ps gene was produced by a transpositional duplication event, which occurred approximately 8.5 million years ago.     

Characterization of thelet-653 gene inCaenorhabditis elegans

A mutation in thelet-653 gene ofCaenorhabditis elegans results in larval death. The lethal arrest is concurrent with the appearance of a vacuole anterior to the lower pharyngeal bulb. The position of the vacuole is consistent with a dysfunction of the secretory/excretory apparatus. Germline transformation rescue experiments were able to position thelet-653 gene to two overlapping cosmid subclones. Sequence data generated from both cDNA and genomic DNA subclones indicated thatlet-653 encodes a mucin-like protein. Our characterization suggests that a mucin-like protein is essential for effective functioning of the secretory/excretory apparatus withinC. elegans.