Question

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Question 24 5 pts 1. Beta-catenin is classified as a proto-oncogene and APC is classified as a tumor suppressor gene. Both are important parts of the Wnt signaling pathway. Describe the relationship between beta-catenin and APC. Explain in detail why they are classified as a proto-oncogene or tumor suppressor gene. 2. Suppose you're working in a cancer research lab and discover a small molecule that can bind the Wnt receptor. If you could target this molecule to tumor cells, would you want the molecule to act as a Wnt receptor agonist or antagonist? Explain your answer.

answer the ones that are straightforward like this one

Answer 1

Solution:

Q24

1. Beta-Catenin and APC are two actively involved proteins in wnt signaling pathway. Active Beta-Catenin enters the nuclues and combine with Turnery Complex Factor(TCF) to activate several developmental responses. Sinc Beta-Catenin is involved in the control of gene expression, dominant gain of fuction mutation to Beta-Catenin induces unwanted gene expression and cellular proliferation. Th APC in the absnce of wnt signal binds and inhibits th Beta-Catenin in the cytosol. APC associate with proteins such as Axin, GSK3, CK1 like proteins to form complex and phosphorylates and inhibits th entry of Beta-Catenin into the cell. Since APC inhibits Beta-Catenin. They are controlling the unwanted proliferation of cells. So they are considered as tumor suppresor proteins.

2. I would prefer the molecule to work as an antagonist. Because if it functions as an agonist it activates the Beta-Catenin entry into the nucleus even in the absence of actuall wnt signal. This may increase the detrimental effects in tumour cells.

3. Except for a mutation in a gene involved for DNA replication.

Q.19

Oncogenes have mutations causing increased activity of the protein. The mutation is called as dominant gain of function mutation unlike recessive loss of function mutation of tumor suppresor genes. Mutation to oncogene results in the increased activity whereas mutation to tumor suppresor causes loss of function.