Question

A positive-strand RNA virus:

a) Has RNA that serves directly as mRNA
b) Has RNA that needs to be transcribed into mRNA
c) Has double-stranded RNA
d) Has RNA that is not involved in translation

Answer 1

The RNA of a positive-strand RNA virus functions directly as mRNA, allowing host ribosomes to immediately translate it into viral proteins. The correct answer is option a).

Step-by-step explanation:

A positive-strand RNA virus has RNA that serves directly as messenger RNA (mRNA). The genomic RNA of such viruses has positive polarity, allowing it to be immediately utilized by host ribosomes for the translation of viral proteins.

In the replication process of positive-strand RNA viruses, replicative intermediates are produced. These intermediates consist of double-stranded RNA (dsRNA) and lead to the creation of multiple RNA strands of negative polarity, which are then used as templates for producing new positive-strand RNA, encompassing both viral mRNA and genomic RNA.

Thus, in the context of positive-strand RNA viruses, the correct answer to the presented question is that the RNA of the virus serves directly as mRNA, option A; this is in line with the organization of the Baltimore classification system for viral genomes.