NOTE 17K: This formula differs from that for additive selection or for selection on haploids (Box 28.2) by the extra term (1/p₀) – (1/p₁). If the initial frequency is very small (p₀ = 10^–6, say), then this is far larger than the last logarithmic term (1/p₀ = 10⁶, but log(1/p₀) = 13.8). Because a recessive allele is rarely exposed to selection when it is rare, it takes a very long time to increase from low frequency.