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Replication of a Positive (+) Sense Strand of Lytic RNA Phage

Why does replication of some RNA viruses require unique processes not found elsewhere? Different kinds of viruses use different molecules for genetic information. There are viruses carrying double stranded DNA, single stranded DNA, double stranded RNA, and single stranded RNA. Some of the RNA viruses are known as retroviruses. They code for a molecule known as reverse transcriptase. Reverse transcriptase synthesizes DNA from an RNA template. The name of the enzyme indicates that the catalyzed reaction is in the reverse direction of transcription. The DNA is then used to transcribe more RNA and make more viruses.

View the animation below, then complete the quiz to test your knowledge of the concept.

1A positive (+) strand of RNA
A)can not function directly as mRNA
B)makes a minus (–) strand of RNA which can then act as mRNA
C)can directly act as mRNA
D)must be double stranded

2In the replication of the positive (+) sense strand of lytic RNA phage, in order to make more positive (+) strands
A)the (+) RNA strand must code for the synthesis of RNA polymerase (replicase)
B)the RNA replicase uses the (+) sense RNA as a template to make (–) strand RNA
C)the (–) sense strand RNA is used to make more (+) strands
D)all of the above

3The negative (–) sense strand of RNA
A)plays no role
B)makes RNA replicase
C)is used to synthesize more + strands
D)acts as mRNA to make viral proteins

4A positive sense strand lytic RNA phage attaches to the cell wall of an E. coli bacterium.

5A phage induced lysozyme lyses the host cell releasing the newly made phage.

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