Cytogenetic approaches to genome mapping

Genetic and physical mapping in mosquitoes: molecular approaches

The genetic background of individual mosquito species and populations within those species influences the transmission of mosquito-borne pathogens to humans. Technical advances in contemporary genomics are contributing significantly to the detailed genetic analysis of this mosquito-pathogen interaction as well as all other aspects of mosquito biology, ecology, and evolution. A variety of DNA-based marker types are being used to develop genetic maps for a number of mosquito species. Complex phenotypic traits such as vector competence are being dissected into their discrete genetic components, with the intention of eventually using this information to develop new methods to prevent disease transmission. Both genetic- and physical-mapping techniques are being used to define and compare genome architecture among and within mosquito species. The integration of genetic- and physical-map information is providing a sound framework for map-based positional cloning of target genes of interest. This review focuses on advances in genome-based analysis and their specific applications to mosquitoes.

FISH digital imaging microscopy in mosquito genomics

The yellow fever mosquito, Aedes aegypti, transmits pathogens that affect both humans and livestock, and has been the focus of extensive research to identify genetic loci that may be useful in control strategies. Fluorescence in situ hybridization (FISH) and digital imaging microscopy have provided a rapid mechanism to populate the physical map with probes derived from genetic markers, cDNAs and recombinant genomic libraries. When the physical and genetic linkage maps are aligned, map-based cloning will allow the rapid isolation of target genomic sequences. The strategy of FISH mapping and the results of initial hybridization studies are reviewed here by Martin Ferguson, Susan Brown and Dennis Knudson. An Ae. aegypti-specific genomic database, which collates data from mapping studies, sequences, references and other relevant information, is also discussed.

Concepts, principles, and applications of selected molecular biology techniques in clinical biochemistry

The myriad molecular techniques that have been developed and are undergoing refinement have advanced our knowledge of disease processes and made available strategies for detection. While the greatest impact of molecular techniques in the diagnostic laboratory has been in the realm of infectious diseases, techniques such as flow cytometry, FISH, and multiplex-nested PCR followed by direct DNA sequencing are increasing the scope of cancer detection and treatment. The facile typing of HLA-class II genes is a major advance in the matching of donors to recipients of organ transplantation. With advances in genosensor technology and robotic automation, molecular biology techniques are clearly poised to enter the diagnostic clinical biochemistry laboratory for multiple applications.

Mouse chromosome-specific painting probes generated from microdissected chromosomes

Using degenerate primer amplification of chromosomes microdissected from banded cytogenetic preparations, we constructed both whole chromosome painting probes for mouse Chromosomes (Chrs) 1, 2, 3, and 11 and a centromere probe that strongly paints most mouse centromeres. We also amplified a Robertsonian translocation chromosome microdissected from unstained preparations to construct a painting probe for Chrs 9 and 19. The chromosome probes uniformly painted the respective chromosomes of origin. We demonstrated the utility of the Chr 11 probe in aberration analysis by staining mutants that we had previously identified as containing a Chr 11 translocation, and in some mutant cell lines we observed chromosome rearrangements not previously detected in stained cytogenetic preparations. The technology of microdissection and amplification applies to all mouse chromosomes or to specific subchromosomal regions and will be useful in mouse genetics, in aberration analysis, and for chromosome identification.

Toward a physical map of Aedes aegypti

Labelled recombinant cosmids were used as in situ hybridization probes to Aedes aegypti metaphase chromosomes. The cosmid probes yielded paired signals, one on each arm of sister chromatids, and they were ordered along the three chromosomes. In total, thirty-seven different probes were mapped to the three chromosomes of Ae. aegypti (2n = 6): twenty-eight to chromosome 1, six to chromosome 2, and six to chromosome 3. These results represent an initial stage in the generation of a physical map of the Ae. aegypti genome.