Non-standard decoding and ribosomal gymnastics

Question 1

Give an example of a plant RNA virus

Answer 1

Tobacco mosaic virus (TMV)

Question 2

What does TMV require?

Answer 2

An RNA-dependent RNA polymerase (‘replicase’)

Question 3

Is TMV a positive or negative strand virus?

Answer 3

(+) strand virus, i.e. RNA acts as mRNA

Question 4

What does the TMV encode?

Answer 4

A coat plus replicase etc.

Question 5

What is the size of the TMV replicase protein?

Answer 5

126 KDa

Question 6

The TMV replicase gene undergoes..

Answer 6

Programmed stop codon readthrough

Question 7

The leaky UAG at the end of the replicase ‘gene’ product =

Answer 7

183 KDa = essential protein

Question 8

What does a ‘slippery sequence’ do?

Answer 8

Causes ribosomes to slip backwards minus 1 frameshift

Question 9

What efficiency does a -1 frameshift have?

Answer 9

50% efficiency

Question 10

Are retroviruses RNA or DNA viruses?

Answer 10

RNA viruses

Question 11

Is RNA translated by retroviruses?

Answer 11

No

Question 12

Viral ssRNA is converted to what in retroviruses?

Answer 12

dsDNA

Question 13

What enzyme do retroviruses need to convert ssRNA to DNA-RNA to dsDNA?

Answer 13

Reverse transcriptase (RT)

Question 14

The dsDNA product produced by the reverse transcriptase of a retrovirus is integrated into..

Answer 14

The genome and expressed normally via transcription and translation

Question 15

What are Gag and Pol products?

Answer 15

Polyproteins

Question 16

What is the ribosome’s PB?

Answer 16

PB = ‘personal best’ as in athletic performance