Choose one of the following three topics for your primary post. Your primary pos
ID: 267353 • Letter: C
Question
Choose one of the following three topics for your primary post. Your primary post should address everything that the instructions call for (for the topic you choose). Your post should also be at least 125 words in length. Additionally, please respond to at least one other discussant on any topic.
Topic 1. Sexual Reproduction in Unicellular Eukaryotes. Watch the instructor's video about "Sexual Reproduction in Unicellular Eukaryotes", which is found in the Instructor Insights section for this week. For a single-celled species to be capable of sexual reproduction, the species must have both haploid and diploid forms
(a) Describe four things that you learned from the video.
(b) Explain how this relates to this week’s lesson.
Topic 2. Apoptosis. Watch the Khan Academy video about apoptosis (“Apoptosis”, n.d.), then address the following issues in your own words:
(a) What is the difference between apoptosis and necrosis?
(b) What is the role of apoptosis in the normal, healthy development of animals?
Reminder: you don't need to cite the Khan Academy video for this topic, but if you use any other sources, you must cite them.
Topic 3. Tumor-suppressor genes versus Proto-oncogenes. This is a library-research topic in which you are required to provide your sources. Mutations in tumor suppressor genes can contribute to or cause cancer, just as mutations in proto-oncogenes can also contribute to or cause cancer. However, tumor suppressor genes are very different from proto-oncogenes.
(a) What is the basic difference between a tumor suppressor gene and a proto-oncogene?
(b) Explain why a gain-of-function mutation to a proto-oncogene (or its promoter) may be associated with increased risk of cancer.
(c) Explain why a loss-of-function mutation to a tumor suppressor gene may be associated with increased risk of cancer.
Explanation / Answer
Topic 3
a. A tumour suppressor gene is the one that slows down the growth of cells, repair DNA during aberrations or lead cells towards apoptosis. Thus, they are considered to be brake checkpoints that keep the cell growth and proliferation under control. Ex: TP53 is a tumour suppressor gene that keeps various cell growth mechanisms in check. Proto oncogene on the other hand are the genes that contribute to cell proliferation and growth and mutation within proto oncogene may lead to uncontrolled growth/proliferation of cells leading to cancer. Ex: Notch1 gene in breast cancer is a proto-oncogene.
b. Gain of function mutation may cause an abnormal increase in proliferation of particular type of cells. This can be explained using an example. R1599P, L1593P or I1681N mutations are various Notch1 gain of function mutations that leads to constitutive expression of Notch1 genes leading to increased T-cell and thus causing T-cell acute lymphoblastic leukemia (T-ALL). Notch1 plays a role in both T-cell and B cell development. However, activation of Notch1 supports T-cell development more leading to an increased number of T-cells.
c.Tumour suppressor genes keep the cell growth and proliferation in check. If there is a loss of function of tumour suppressor genes,then uncontrolled growth and cell proliferation may take place leading to cancer. Ex: p53 mutation or loss of function is found in several cancers that may affect several processes like apoptosis , cell cycle checkpoint control etc.