Tobacco smoke is a complex mixture of chemicals, known to cause genetic and epigenetic aberrations (1). The genetic aberrations caused by tobacco smoke are detected in both the directly exposed (e.g. lung) and unexposed tissues (e.g. blood) (2). Most of the previous studies have looked at the germline mutation with a rationale that a vast majority of cells in the human soma are genetically identical and is stable across the human lifespan. However, the field of human genetics is increasingly recognising that genetic variation acquired during life (i.e., post-zygotic changes) (3). A recent study by Dumanski et al. found that men who smoke are thrice more likely to show post-zygotic loss of Y chromosome (LOY) in their blood cells suggesting that LOY was by far the most common postzygotic mutation (4). However, the differential impact of parental smoking on LOY in male offspring remains unexplored.
The Avon Longitudinal Study of Parents and Children provides a unique opportunity to delineate the genetic impact of parental smoking on offspring sex chromosomes at birth and to study the persistence of these events longitudinally.

References:
1. Humans IWGotEoCRt. Personal habits and indoor combustions. Volume 100 E. A review of human carcinogens. IARC Monogr Eval Carcinog Risks Hum 2012;100(Pt E):1-538.
2. Lee KW, Pausova Z. Cigarette smoking and DNA methylation. Front Genet 2013;4:132.
3. Dumanski JP, Lambert JC, Rasi C, Giedraitis V, Davies H, Grenier-Boley B, et al. Mosaic Loss of Chromosome Y in Blood Is Associated with Alzheimer Disease. Am J Hum Genet 2016;98(6):1208-19.
4. Dumanski JP, Rasi C, Lonn M, Davies H, Ingelsson M, Giedraitis V, et al. Mutagenesis. Smoking is associated with mosaic loss of chromosome Y. Science 2015;347(6217):81-3.