Breast Cancer

There are two main types of breast cancer which are due to a single gene mutation BRCA-1 and BRCA-2; these are both tumour-suppressor genes. These genes are key parts of the DNA-break repair systems, therefore they are unable to repair DNA where the homologous chromosome is providing template repair. If a women inherits one mutated allele of BRCA-1, they have a 60% probability of developing breast cancer by the age of 50, compared with a 2% probability if a women has two normal alleles. These statistics lend themselves to the genetic influence on cancer. However most types of breast cancer are due to a several low penetrance genes instead as cancer is an example of a polygenic disease, therefore it is a disease where many genes are involved.

The genetic prediction of breast cancer susceptibility is varied depending on which type of breast cancer we are talking about, advice can be given to those with a family history due to BRCA-1 or BRCA-2. But for other types of breast cancer it is hard to advise women on their risk due to so many factors and the effects of individual’s polymorphisms  .