Answer to Question #168653 in Molecular Biology for Jasmine Elfaqir

Question #168653

Judy did a little research on skin cancer on the Internet before the visiting her doctor next morning. She found out what happened with other people, that were significantly older than she. It didn’t make sense that this would happen to her - she was only 20 years old!

The articles talked about how the sun’s ultraviolet light can be cause of DNA mutations. Accumulated DNA mutations over the years can cause genes super-activation. Judy was really grateful for the college biology course she attended. She knew that DNA was hereditary material that acted as a “plan” for everything our cells did, and that the gene was a piece of DNA that contained instructions for synthesizing a single protein. However, she should ask the doctor about these genes.

During the examination Dr. O'Brien was silent, looking at the mole on her leg. Finally, he said kindly: “I want to do a biopsy. All this means that we will remove your mole and look at the cells under a microscope and determine if they look abnormal. "

Judy said with tears: “You mean you can tell me that I have a tumor just by looking at some cells?”

 “It is very possible that your cells will look completely normal. A tumor is not necessarily the same as cancer. ” She looked embarrassed, so he continued: “A tumor means that the cells divide and gather in the same mass. But not all tumors automatically become malignant and life-threatening. A benign tumor is a mass of normal cells. These tumors are not considered as a cancer, and they are usually easily treated - we just remove them”, Dr. O'Brien replied.

The doctor smiled and seemed pleased that Judy read about it herself. “Let's remember! You see, we have tens of thousands of genes in our cells, but this does not mean that mutations in just any of them will lead to cancer. Genes that become mutated and can cause cancer have a specific type called cell cycle genes. Each person has a set of cell cycle genes in each of his cells that encode cell cycle proteins.  In normal healthy cells, cell cycle protein formation is tightly controlled, activating proteins are produced only when we really need more cells, and inhibitory proteins appear only when we don't need more cells. However, mutations in these genes can eliminate this tight regulation and lead to uncontrolled cell division. This is what happens in many types of cancer: the normal cell process, cell division, that is no longer properly controlled. ”

Judy thought for a second. “Okay, but you still haven't said what proto-oncogenes are.”


Issues for discussion:

1. What genes is Judy talking about? What are these genes called?

2. What are the functions of these genes in the cell? Explain.

3. List several genes that belong to this group.

4. In addition to these genes, mutation of what other genes leads to cell transformation?

5. Explain the mechanisms of conversion of proto-oncogenes into an oncogene.

6. What properties are characteristic of benign and malignant tumors.  Describe.

7. What stages of malignant transformation of cells do you know? Describe each stage.



Expert's answer

1) Judy talk about cell cycle regulating genes. There is two class of genes proton-oncogenes and tumor suppressor gene.

2) proto-oncogenes progress cell cycle increases the number of cells and hence growth.

Tumor suppressor genes is inhibitory to progression of cell cycle. Hence inhibit growth.

3 ) EF2 ,cyclin A , cyclin B are cell cycle regulator genes

4) apoptotic genes cause apoptosis of cell hence cell death and anti-apoptotic genes cause inhibition of apoptosis hence cell survival.

5) point mutation- any nucleic acid sequences change at single site hence gene become active persistently.

Deletion mutation - and potion of nucleic acid sequences changes hence gene become active persistently.

In short any mutation which cause the gain of function mutation lead to formation of oncogenes from proto-oncogenes.

6) Benign tumor slowly increase in size.

Benign tumor does not invade surrounding tissue.

Benign tumor is not metastasized.

Benign tumor is less lethal.

Benign tumor boundary is clear.

Malignant tumor rapidly increase in size.

Malignant tumor invade surrounding tissue.

Malignant tumor is mostly lethal

Malignant tumor metastasized.

Malignant tumor boundary from normal tissue is not clear.

7) Stages of malignant tumor

Initiation-any mutation that cause formation of mutated cell and cell increase proliferation in number.

Promotion- any stimuli which support these mutated cell and cause increase growth of cells in number.

Progression- process in which cells is now self sufficient to grow enormously.

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