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8 Cards in this Set

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How are the RNA viruses different from the Retro virus.
The retro viridae carry with them a unique enzyme called reverse transcriptase. It is an RNA dependent DNA polymerase that converts the viral RNA into DNA.
Can Retroviruses cause cancer in the cells they infect. Some retro viruses carry oncogenes in their genomes. TRUE/FALSE
TRUE.
What is contact inhibition?
Normal cells have strict growth control. They divide an exact number of times with exact timing, depending on the type of cell.Normal cells are grown on a plate of nutrient media, they form a single layer and stop dividing when they touch each other.
malignant cells lose contact inhibition and pile up in vitro. They become immortal.
How do oncogenes cause cancer?
The normal cell has receptor proteins in the cell membrane that regulate cell growth. Growth factors(mitogens) bind to these receptors to regulate growth. An example would be an insulin receptor, the " epidermal growth factor"(EGF) and the "platelet derived growth factor".
Mitogen stimulation of these receptors causes intracellular phosphorylation of tyrosine. Phosphotyrosine then acts as an intracellular growth messenger.
Can the Rous virus cause cancer?
Yes. The Rous sarcoma virus oncogene(src) encodes a transmembrane protein that also phosphorlates tyrosine, but at ten times the normal rate. The erb-B oncogene that causes cancer in chickens encodes a protein similar to the EGF recetor.
Because most of the retroviridae isolated to date cause either leukemia or sarcoma in their vertebrate hosts, they are sometimes called leukemia sarcoma viruses. TRUE/FALSE
TRUE.
What can be said of acute transforming viruses/
Some retroviridae, the acute transforming viruses, carry intact oncogenes within their viral genome, which when integrated into the host DNA cause malignant transformation. This integration is facilitated by "integrase".
The acute transforming virus was discovered in 1911 when Peyton Rous injected cell free filtered material from a chicken tumor into another chicken. The recipient developed a tumor. TRUE/FALSE
TRUE. It is called a Rous sarcoma virus, which possesses an oncogene called src.