In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA.
The table below shows the results of testing five viruses for nuclease specificity, the ability of the virus to act as an mRNA, and presence (+) or absence (-) of its own viral polymerase.
Virus Nuclease
Sensitivity
Genome as mRNA
Polymerase
A
Dnase
-
-
B
Rnase
+
-
C
Dnase
-
+
D
Rnase
-
+
E
Rnase
+
-
1) Given Baltimore's scheme, a positive sense single-stranded RNA virus such as the polio virus would be most closely related to which of the following?
A) T-series bacteriophages
B) retroviruses that require a DNA intermediate
C) single-stranded DNA viruses such as herpes viruses
D) nonenveloped double-stranded RNA viruses
E) linear double-stranded DNA viruses such as adenoviruses
Answer: B
2) Based on the above table, which virus meets the Baltimore requirements for a retrovirus?
A) A
B) B
C) C
D) D
E) E
Answer: D
3) Based on the above table, which virus meets the requirements for a bacteriophage?
A) A
B) B
C) C
D) D
E) E
Answer: A