We explained three ways in which viruses could transform human cells, leading to

Question

We explained three ways in which viruses could transform human cells, leading to the formation of tumors.

A. Using diagrams to illustrate the location of the viral genome, explain all three, noting which type of human gene is altered, and how the alteration leads to possible tumor formation. The vocabulary words “provirus” and “plasmid” should appear in your answers.

B. Describe TWO experiments you could use to determine whether or not a provirus was integrated at a specific place within a human host cell.

Explanation / Answer

1. The type of transformations that alter the human genome are as follows:

a) Cytocidal - changes in cell morphology and physiology. Changes in morphology include fusion with adjacent cell and synthesis of cytoplasmic inclusion bodies. Physiological changes consist of inhibition of Synthesis of DNA. RNA AND proteins . These are of two types ABORTIVE , that do not produce infectious viruses and PRODUCTIVE that b) Peristent - three types that include chronic , latent and slow. LATENT - minimal to no viral genome expression. CHRONIC- Similar to acute cytocidal infections but limited number of additional viruses produced. SLOW - longer incubation of the virus with no changes involved at subcellular level

c) Transforming - Have both abortive and restrictive infections . Also constitutes of cytocidal and persistent type and are thus known as the broadest of the viral transformations. This can be done by both DNA viruses and RNA viruses produce additional infectious viruses, causing mutations in the body with unlimited cell replications. These infections inactivate the Tumor suppressor proteins and are also involved in impairment of cell cycle regulation.

During transformation, the viral DNA enters the host cell . In causing tumours by viruses, the method is known as viral oncogenesis . Some viruses that commonly cause oncogenesis are HPV, T-cell Leukemia virus type I, and hepatitis B. Acute transformations induce rapid growth of tumours because they are carriers of viral oncogenes. Non acute transformations activate proto oncogenes as they do not carry an oncogene of themselves , they activate the long terminal repeats in the proto oncogenes, thus inducing a slow tumour formation .

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