Table showing degrees of relatedness that have relevance to a family history pedigree

The degree of relatedness is helpful in determining the amount of genetic material that is likely to be shared with the proband. First-degree relatives share approximately 50% of their DNA, second-degree relatives share approximately 25% of their DNA, and third-degree relatives share approximately 12.5% of their DNA. Refer to UpToDate for further information about pedigree interpretation and genetic risk assessment.