Genetic screening is recommended when a specific cancer appears to run in a family. BRCA and Lynch syndrome are two conditions, that when inherited, predispose someone to developing a number of different cancers. 

BRCA 1 and BRCA 2 are tumour suppressor genes. When they function normally they stop cells in the breast, ovary and other tissues from dividing too rapidly and also repair errors that happen when cells do divide. Mutations in these genes result in a higher risk of developing cancer of ovary and breast. 

Lynch syndrome predisposes to a number of cancers - most commonly colon, uterine and ovarian cancer. Lynch syndrome arises due to errors in a process called mismatch repair. Mismatch repair is a process of DNA repair that typically involves four different genes.