Consider the following statements: 1. Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes. 2. Common cold is sometime caused by an adenovirus whereas AIDS is caused by a retrovirus. Which of the statements given above is/are correct?

Answer: B. Only statement 2 is correct. Statement 1 is WRONG. The claim REVERSES the actual genomic structure of adenoviruses and retroviruses: - ADENOVIRUSES have a DOUBLE-STRANDED DNA (dsDNA) GENOME — NOT single-stranded. - RETROVIRUSES have a SINGLE-STRANDED RNA (ssRNA) GENOME — NOT double-stranded DNA. They use the enzyme REVERSE TRANSCRIPTASE to convert their RNA into DNA inside the host, which then integrates into the host genome. So both halves of statement 1 are factually inverted. Statement 2 is CORRECT. - ADENOVIRUSES are a well-known cause of UPPER RESPIRATORY TRACT INFECTIONS including SOME CASES OF THE COMMON COLD (alongside rhinoviruses, coronaviruses, parainfluenza viruses, respiratory syncytial virus). Adenovirus is one of the >200 viruses associated with common-cold-like symptoms. - HIV (HUMAN IMMUNODEFICIENCY VIRUS), the cause of AIDS, IS A RETROVIRUS belonging to the genus Lentivirus, family Retroviridae. HIV's ssRNA is reverse-transcribed into DNA, integrated into the human T-cell genome, leading to T-cell depletion and immunodeficiency. The adenovirus is also notably used as the VIRAL VECTOR in many COVID-19 vaccines (Covishield, J&J, Sputnik), because its dsDNA genome can carry transgenes safely. Source: NCERT Class 12 Biology 'Human Health and Disease' / Class 11 Biology 'Biological Classification' (Viruses) / WHO HIV documentation.