Question

Part III: Dr. Hernandez sits down with Ann and her partner. The doctor is sorry to report that Ann has breast cancer; however, because it was caught early and responds to estrogen and progesterone, the prognosis is good. At this point it looks like the cancer is stage 1. However, as Ann is young, the doctor wants to perform a couple tests. The first test is a genetic sequencing test for BRCA1 and BRCA2, as well as testing for other genes known to increase the risk of cancer. The other test is an Oncotype DX test on the tumor cells. This is a gene expression test, where the results correlate with how aggressive the cancer cells are. Ann is overwhelmed, but wants to do everything she can to get rid of this disease.

2. Also, as a result of your discussion, you know that the expression of genes can change in cancerous cells versus noncancerous cells. The Oncotype test will look at the expression levels of several genes in her tumor cells by looking at the mRNA produced.

a. What role does mRNA play in the flow of information in the cell? (Hint: Remember the central dogma of molecular biology.) Please include the basic flow of information in the cell. INSERT ANSWER

b. Cancer cells and noncancerous cells may have almost identical DNA; however, gene expression can change. Explain the concept of differential gene expression using cancer versus noncancerous cells as an example. INSERT ANSWER

c. This Oncotype test uses microarray analysis to determine gene expression. Explain to Ann what a microarray is. INSERT ANSWER d. The results of Ann’s Oncotype test showed a decrease in the expression of BRCA1. How can this decrease lead to an increase in cell division? (Hint: What is the normal role of BRCA1?) INSERT ANSWER

Answer 1

2a. ANS: MRNA is said to be a messenger that travels from the nucleus, it is in charge of synthesizing proteins and the regulation of said proteins. In regards to the central dogma, it is a description of the process of transcription and translation of genes into proteins. In eukaryotes (Anderson 2017), DNA is transcribed and here we see pre-mRNA, next, RNA processing occurs and MRNA is generated, the mRNA will exit the nucleus and translate in the cytoplasm (OpenStax 2013).

2b. ANS: To review, “cancer is the disease of altered gene expression. There are many proteins turned off or in that dramatically alter the overall activity of the cell (OpenStax 2013).

2c. ANS: A microarray is a machine used to show whether the DNA of a person contains a mutation in their genes.

2d. ANS: A decrease in expression of BBCA 1 is going to lead to an increase in cell division because, normally BRCA1 is responsible for negative regulation of the mammary epithelial cell growth (Vanderbilt). When this gene is decreased the cells grow too much and too fast, causing breast cancer