Correction to: Nature Reviews Genetics https://doi.org/10.1038/nrg1960, published online 01 October 2006.

The authors regret an error in Figure 1 and its legend. The last sentence of the legend should be “The calculation of θ is provided below the figure using δ or Δ.” The equation “θ = k1/2 + k1/4” should be changed to “θ = k2/2 + k1/4, provided X, Y are not inbred.” In the example scenario, X, Y are full sibs with first-cousin parents and so they are inbred: their coancestry θ does not follow from the expression involving only k. The authors are grateful for having their error noticed by a reader.