Mapping quantitative trait loci with extreme discordant sib pairs: sampling considerations

Area of Science:

• Human genetics
• Statistical genetics
• Genomic research

Background:

• Quantitative trait loci (QTL) mapping is crucial for understanding genetic contributions to complex traits.
• Extreme discordant sib pairs (EDSPs) have been proposed as a powerful design for human QTL mapping.

Purpose of the Study:

• To determine the necessary sample sizes and screening numbers for effective EDSP studies.
• To provide formulas for adjusting sample size calculations based on statistical parameters and marker characteristics.

Main Methods:

• Statistical power calculations for QTL mapping using EDSPs.
• Formulas for sample size adjustment in multipoint sib-pair analysis.
• Assessment of genetic effect size detectable with realistic sample sizes.

Main Results:

• The study presents specific sample size requirements for achieving desired statistical power in EDSP designs.
• Formulas are provided to adjust sample sizes for varying significance levels, power, marker density, and informativeness.
• The most powerful design, EDSPs, can detect genetic effects accounting for approximately 10% of trait variance with realistic sample sizes.

Conclusions:

• Extreme discordant sib pairs represent a highly effective strategy for mapping quantitative trait loci in human populations.
• The presented calculations and formulas facilitate the practical design and implementation of EDSP studies.
• This approach enables the detection of relatively small genetic effects, advancing our understanding of complex trait genetics.