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Two common polymorphisms in the APO A-IV coding gene: their evolution and linkage disequilibrium.
M I Kamboh1, R F Hamman, R E Ferrell
1Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pennsylvania 15261.
Genetic Epidemiology
|January 1, 1992
Summary
Human apolipoprotein A-IV (APO A-IV) genetic variation was studied at two common polymorphic sites. Researchers identified three common haplotypes and significant linkage disequilibrium, suggesting independent mutation origins.
Area of Science:
- Human Genetics
- Molecular Biology
- Biochemistry
Background:
- Human apolipoprotein A-IV (APO A-IV) exhibits known polymorphisms at codon 360 (glutamine/histidine) and a newly identified one at codon 347 (threonine/serine).
- Understanding genetic variation in APO A-IV is crucial for its role in lipid metabolism and cardiovascular health.
Purpose of the Study:
- To investigate the genetic variation and allele frequencies at the APO A-IV codon 347 polymorphism in a human population.
- To determine the haplotypes and linkage disequilibrium between the codon 347 and codon 360 polymorphic sites in APO A-IV.
Main Methods:
- DNA samples from 192 unrelated individuals were screened for codon 347 variation using a polymerase chain reaction (PCR) based assay.
- Plasma samples were analyzed by isoelectric focusing (IEF) to determine allele frequencies at the codon 360 polymorphism.
- Genotype data from both sites were used to assign haplotypes and assess linkage disequilibrium.
Main Results:
- Allele frequencies at codon 347 were A-IV*A (0.81) and A-IV*T (0.19), with an average heterozygosity of 0.31.
- Allele frequencies at codon 360 were A-IV*1 (0.922) and A-IV*2 (0.078), with an average heterozygosity of 0.14.
- Three of the four possible haplotypes (A1, T1, A2) were observed, with frequencies 0.732, 0.190, and 0.078 respectively, and an overall average heterozygosity of 0.42. Significant linkage disequilibrium was detected between the two sites.
Conclusions:
- The study characterizes the genetic variation at two common polymorphic sites in human APO A-IV.
- The observed linkage disequilibrium and allele frequencies suggest that the A2 and T1 haplotypes may have arisen independently from the common A1 haplotype through separate mutations.