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Sample size required to detect linkage between a marker and QTL

Claudio Lopes de Souza Jr

Departamento de Genética, ESALQ-USP, Caixa Postal 83, 13418-900 Piracicaba, SP, Brasil

ABSTRACT

The sample sizes required to detect linkage between a marker and QTL for an unreplicated F₂ population, and for replicated F_3:2, F_4:3 and recombinant inbred lines were investigated. The F test with P ≤ 0.01 in the analysis of variance was used to detect linkage. The expectations of the mean squares were manipulated to express the F ratio in terms of the distance between the marker and the QTL (r), the heritability (h²) and the level of the dominance of the trait, the sample size, and the ratio f ≈ σ²_Aq/ σ²_A. The sample sizes were estimated from the F test. As r decreases, and h² and f increase, the sample size decreases; and as r increases and h² and f decrease, the sample size increases.

Keywords: Sample size; Linkage; QTL.

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