Consider the following statements: 1. Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes. 2. Common cold i

1. A. 1 only
2. B. 2 only
3. C. Both 1 and 2
4. D. Neither 1 nor 2

Answer: B

Explanation

Adenoviruses are medium-sized (90–100 nm), non-enveloped, icosahedral viruses composed of a nucleocapsid and a linear, double-stranded DNA (dsDNA) genome. Viruses of the family Adenoviridae infect vertebrates, including humans. In a double stranded RNA form, retroviruses infect a host cell with their genome, and then are reverse transcribed into double stranded DNA, with the DNA then integrated into the home cell genome. The virus thereafter replicates as part of the host cell’s DNA. Hence statement 1 is not correct. Adenoviruses are common viruses that cause a range of illness. They can cause cold-like symptoms, fever, sore throat, bronchitis, pneumonia, diarrhea, and pink eye (conjunctivitis). HIV is called a retrovirus because it works in a back-to-front way. Unlike other viruses, retroviruses store their genetic information using RNA instead of DNA, meaning they need to ‘make’ DNA when they enter a human cell in order to make new copies of themselves. Hence statement 2 is correct.