NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE Part IlI Gene Expression and
ID: 253173 • Letter: N
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NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE Part IlI Gene Expression and Disease Unfortunately, the results from Lee's biopsy are in and it appears that he has adrenocortical carcinoma (ACC). Fortunately, Dr. Aikenhed (who, in addition to her clinical practice in the area of oncology also conducts research) is on the cutting edge of developing treatments for this condition. She is part of a consortium of researchers that are trying to catalog all of the different genes that may be involved in adrenal cancer. This will help physicians and scientists to discover drugs to target specific cancer-contributing gene products. Cancer genes can be categorized in many different ways. Proto-oncogenes produce proteins that are involved in promoting the cell cycle. Mutations in these genes tend to cause either an over-production of protein (over-expression) or a protein to be constitutively active (pushing the cell cycle forward even in the absence of a signal to divide (e.g. Tumor suppressor genes, on the other hand, put the brakes on the cell cycle, usually at key checkpoints. Mutations in tumor suppressor genes that contribute to protein (under-expression) at all. A mutation like this could allow a damaged or rogue cell to divide when it shouldn't. carcinogenesis ca n cause either abnormally low levels of protein or no Genome-maintenance genes can also play a role in cancer and they include the telomerase gene (which helps extend the life of a chromosome and, consequently, the number of cell division cycles that it can undergo) and DNA repair genes (which keep the level of mutations in all genes low). Dr. Aikenhed and her colleagues use microarrays containing the most common genes implicated in ACC to analyze gene expression (both over-or under-expressed genes) in cancer samples compared to normal tissue. To understand more about this technique, you decide to review the basics of microarray analysis by going through slides 1-9 at this website:Explanation / Answer
Answer 1. In patient's cell, majority of the gene expression are similar to the normal cell (as indicated by yellow color). However, one gene TP53, is labelled green indicating that the gene expression is lower than the control cells.
Answer 2. Misense mutation
Justification : data available on http://p53.iarc.fr/SelectedStatistics.aspx
Answer 3. Missense mutation is a type of point mutation. In this type of mutation, a single nucleotide changes resulting in formation of different amino acid. For example, a missense mutation from GAG to GUG will result in the synthesis of amino acid valine rather than glutamic ACID. This mutation causes sickle-cell anaemia.
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