Genes and disease risk: A closer look

SNPs occur when chromosomes are scrambled through recombination over many generations.

If a SNP (see “A”) on the ancestral chromosome increases the risk of a disease—cancer, for example—any offspring who inherit that chromosomal segment will also be at increased risk.

Suppose a particular SNP signals a significant increase in breast cancer risk. What might be done to prevent the disease? Is it useful and cost-effective to screen healthy women for the variant? Researchers have only just begun to explore questions like these.

illustration: Ida Floreak/Anne Hubbard

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