Cell Transformation By DNA Viruses

Question 1

The discovery of how _______ induce mutation and transform the cell was made first of ______ viruses

Answer 1

Viruses ; DNA

Question 2

Which was the first DNA virus to be studied for its transforming abilities?

Answer 2

SV40, a small double stranded DNA tumour virus

Question 3

Which two forms of infection does SV40 sustain? Describe them. In which animals does each occur?

Answer 3

Latent (in Macaco Rhesus monkeys) - no virus can be recovered from these cultures
Lytic (in African monkeys) - cells display cytopathic effects typical lytic cycle and large vacoules. Thousands of viral particals are produced

Question 4

Does SV40 cause cell transformation in macaco’s cells or african monkey cells?

Answer 4

No, it does not tranform either of the cells

Question 5

Which cells does SV40 transform?

Answer 5

When SV40 is introduced into rat/mouse/hamster cells there is no lytic cycle but these cells become transformed at low frequency

Question 6

Describe how SV40 can act in different cells

Answer 6

• Lytic cycle producing viral particles
• Transforming cells at low frequency
• Frustrated, latent cycle. No viral particles produced, but the virus persists

Question 7

Describe the experiment which found that the DNA of SV40 was integrated into the host genome

Answer 7

The viral DNA was radiolabelled and the virus was introduced into non-permissive cells (cells which don’t allow the full lytic cycle but become transformed).

The DNA is extracted and there is unequivocable proof that SV40 DNA is integrated into the genome of the host cell

Question 8

In which year was it understood how transformation by DNA viruses occurs?

Answer 8

1968