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Beta-globin gene cluster haplotypes in Hb C heterozygotes
C A Talacki1, E Rappaport, E Schwartz
1Cardeza Foundation for Hematologic Research, Department of Medicine, Thomas Jefferson University, Philadelphia, PA 19107.
Hemoglobin
|January 1, 1990
Summary
The beta C mutation, linked to hemoglobin C (Hb C) disease, likely originated from a single source, evidenced by a common genetic marker. However, a rare exception suggests a potential second origin for this mutation.
Area of Science:
- Molecular Biology
- Genetics
- Hematology
Background:
- Previous research suggested a single origin for the beta C mutation based on a rare beta A chromosome haplotype lacking a Hpa I recognition site 3' to the beta-globin gene.
- This unique haplotype has been a key characteristic used to support the hypothesis of a solitary emergence of the beta C allele.
Purpose of the Study:
- To investigate the origins and haplotype characteristics of the beta C mutation in individuals with hemoglobin C (Hb C) related conditions.
- To determine if the previously identified unique beta C haplotype is consistently present across different Hb C genotypes.
Main Methods:
- Haplotyping analysis was performed on beta C alleles from 40 patients with Hb SC, 11 with Hb AC, and one with Hb CC.
- Complete haplotyping was achieved for 44 beta C alleles, with additional 3' haplotyping conducted on four others.
Main Results:
- The study confirmed the predominance of a unique beta C haplotype characterized by the absence of the Hpa I recognition site, supporting previous findings.
- However, one patient homozygous for Hb C presented an atypical beta C haplotype that included the Hpa I site, deviating from the common pattern.
Conclusions:
- The findings largely support the prevailing theory of a single origin for the beta C mutation, linked to a specific haplotype.
- The identification of an atypical haplotype in one case raises the possibility of a secondary origin for the beta C mutation, warranting further investigation.