A highly polymorphic locus in human DNA revealed by cosmid-derived probes.

Area of Science:

• Genetics
• Molecular Biology
• Genomic Research

Background:

• Human gene mapping requires highly informative marker loci with significant heterozygosity.
• Cosmids from human genomic libraries offer a potential source for such genetic markers.

Purpose of the Study:

• To develop an efficient method for screening human genomic cosmids to identify those rich in restriction fragment length polymorphisms (RFLPs).
• To generate novel polymorphic marker loci for enhanced human gene mapping.

Main Methods:

• A rapid screening method was developed using whole cosmids as probes against Southern transfers of genomic DNA.
• Prehybridization with excess nonradioactive genomic DNA was employed to block hybridization to repetitive sequences, enabling focus on single-copy regions.
• Cosmids identified as homologous to RFLP-rich regions were further processed to isolate single-copy probes.

Main Results:

• One cosmid yielded three single-copy probes that collectively identified seven distinct polymorphic loci.
• Out of 56 unrelated individuals tested, 52 (approximately 93%) were found to be heterozygous at one or more of these newly identified marker loci.

Conclusions:

• The developed cosmid screening method is effective in identifying human genomic regions rich in RFLPs.
• The identified polymorphic loci represent valuable new markers for facilitating human gene mapping and genetic studies.
• This approach significantly increases the availability of highly heterozygous markers for genetic analysis.