Inheritance of a mutated BRCA1 gene, sometimes known as the breast cancer gene, increases the risk of breast cancer from about 12.5% for non-carriers to about 65% for carriers. People who carry this mutation also have increased risk for ovarian cancer. However, this is just an increased risk; it does not guarantee a person will get breast cancer, just as lack of BRCA1 or BRCA2 mutations does not guarantee a person will not get breast cancer. In addition, most breast cancer tumors have decreased expression of BRCA1, even in people who do not carry a mutated gene. Your goal in this discussion is two-fold. First, draw conclusions as to why inheritance of BRCA1 (or any other gene associated with increased risk of cancer) does not generally lead to 100% risk of getting that cancer (and alternatively, why people without the mutation still get cancer). Second, use your knowledge of gene expression to explain why some people without the BRCA1 mutation have decreased expression of this gene in the tumor compared to normal cells.
1 Conduct some research on BRCA1 and the genetics of cancer (remember to write down your sources).
2 Read the following article, “The Epigenetics of Breast Cancer.”
3 Start your discussion post with an explanation of how inheritance of a gene that increases risk of cancer does not lead to the certainty of cancer. In this paragraph, include a discussion of the steps that need to occur from a cellular and genetic perspective for cancer to occur.
4 After reading the article, answer the following questions in a paragraph. You can also use your text and other sources, just remember to write down any sources you use and include them as references in your post.
◦ Briefly describe differential gene expression in cancer cells versus noncancerous cells.
◦ What is epigenetics, and how does it relate to gene expression?
◦ Would sequencing the DNA of a cancerous tumor allow a doctor to know whether there were changes in gene expression in a tumor?
◦ In your third paragraph, describe two methods you could use to study gene expression in cancerous versus noncancerous cells. Based on the article above, what patterns might you look for to predict whether a tumor was cancerous?
5 Finally, reflect on DNA sequence analysis. If given the choice to determine whether you had the BRCA1 gene, would you do it? What are the benefits and the risks?