Several recently published papers address limitations of existing genome sequencing approaches in distinguishing haplotypes. By starting with a very small number of cells and using a special sample preparation workflow to deliver a single copy of a chromosome to a well in a microtiter plate, Peters et al. report a whole-genome sequencing strategy that can differentiate the paternal chromosome from the maternal. Two reports by Fan et al. and Kitzman et al. also describe non-invasive haplotype analysis of a fetus by sequencing fetal DNA circulating in the mother's bloodstream. Whereas Kitzman et al. required knowledge of both the mother's and the father's genome to sequence the fetal genome, the strategy of Fan et al. dispenses with the need for a paternal sample.

Peters, B. et al. Accurate whole-genome sequencing and haplotyping from 10 to 20 human cells. Nature 487, 190–195 (2012).

Fan, H.C. et al. Non-invasive prenatal measurement of the fetal genome. Nature advance online publication, doi:10.1038/nature11251, 4 July 2012.

Kitzman, J. et al. Noninvasive whole-genome sequencing of a human fetus. Sci. Transl. Med. 4, 137ra76 (2012).