Which of the following statements is not true for retroviruses?

Explanation

Retroviruses are unique viruses with a complex life cycle, and their features help explain which statements are true or false. Statement (a) is false because retroviruses indeed have a DNA stage in their replication cycle. After infection, they use the enzyme reverse transcriptase to convert their RNA genome into DNA, which integrates into the host cell's chromosomes. Statement (b) is true because retroviruses encode RNA-dependent DNA polymerase, better known as reverse transcriptase, which is essential for converting viral RNA into DNA. Statement (c) is also true since retroviruses carry RNA as their genetic material inside mature virions, which is used as a template after infection. Finally, statement (d) is true because some retroviruses, such as HTLV-1, are oncogenic, meaning they can disrupt normal host cell growth regulation and potentially cause cancers like adult T-cell leukaemia. These features distinguish retroviruses from other types of viruses.