Oncogenes and tumor suppressor genes

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Oncogenes and tumor suppressor genes

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Oncogenes and tumor suppressor genes

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USMLE® Step 1 style questions USMLE

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A 65-year-old man comes to the physician for follow-up after his leukocyte count was found to be highly elevated. Karyotyping was ordered for this patient and translocation between chromosome 9 and 22 was found. Which of the following is most likely to happen as a result of this translocation?  

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First Aid

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Acute lymphoblastic leukemia (ALL) p. 440

oncogenes and p. 222

Antiapoptotic molecule

oncogene product p. 222

Breast cancer

oncogenes and p. 222

Burkitt lymphoma p. 437

oncogenes and p. 222

Chronic myelogenous leukemia (CML) p. 440

oncogenes and p. 222

Colon cancer

oncogenes and p. 222

Gastric cancer p. 388

oncogenes and p. 222

Lung cancer p. NaN

oncogenes and p. 222

Lymphoma

oncogene for p. 206, 222

Medullary thyroid carcinomas p. 349, 359

oncogenes and p. 222

Melanoma

oncogene p. 222

Neuroblastomas p. 357

oncogenes and p. 222

N- myc oncogene p. 357

Non-Hodgkin lymphoma p. 436, 437

oncogenes and p. 222

Oncogenes p. 222

Ovarian cancer

oncogenes and p. 222

Pancreatic cancer p. 404

oncogenes and p. 222

Receptor tyrosine kinase

as oncogene product p. 222

Tyrosine kinase

as oncogene product p. 222

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Transcript

Oncogenes and tumor suppressor genes are classes of genes that code for various proteins that are involved in the progression of the cell cycle.

Oncogenes are actually mutated versions of proto-oncogenes, which are normal genes in charge of positive regulation of the cell-cycle.

So the protein products of proto-oncogenes stimulate cell growth and division - they’re like a gas pedal in a car.

Tumor suppressor genes, on the other hand, are in charge of negative regulation of the cell cycle, so their protein products stop its progression and promote apoptosis or cell death.

Tumor suppressor genes are involved in DNA repair mechanisms and inhibiting transcription factors that try to push the cell along in the cell cycle - so they’re like the brake pedal in a car.

Now, the cell cycle is the series of events that a cell goes through as it changes from being one cell into two daughter cells.

The cell cycle has two phases: interphase and mitosis. Interphase is comprised of the G1 phase, during which the cell grows and performs its cell functions, the S phase, during which DNA is replicated, and the G2 phase, during which the cell grows again before entering mitosis.

At the end of G1 and G2, there are cell cycle control points called the G1 and G2 checkpoints, where the cell checks to see if there’s any DNA damage.

The main control point is the G1 checkpoint.

If it turns out that there is DNA damage, then the cell can either enter a non-dividing state called the G0 phase, where the DNA repair mechanisms try to fix the problem, or the cell can self-destruct in a process called apoptosis.

Summary

Oncogenes and tumor suppressor genes are types of genes that play a role in the development of cancer. Oncogenes are mutated versions of proto-oncogenes, which normally regulate and promote the cell cycle to progress. Oncogenes end up promoting uncontrolled cell growth and division, causing normal cells to become cancerous. On the other hand, tumor suppressor genes are genes that code for protein products that regulate and slow down the cell cycle, and also promote apoptosis, which is programmed cell death.

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