Imagine that you study a new type of cancer C, which is highly unusual in that it is caused solely by exposure to a particular toxic chemical X found in slugs. Whether an individual develops cancer after ingesting slugs is not controlled by their genetic makeup; rather, 100% of individuals who have ingested at least one slug develop the cancer shortly thereafter. Imagine further that whether individuals eat slugs is controlled by a gene G with two alleles G1 and G2 that co-exist in the population. Individuals homozygous for G1 find slugs yummy and eat them for breakfast every day; all other individuals do not eat any slugs. What heritability would you find if you studied cancer C as a trait in that population?
