Question

Which of the following statements is not true for retroviruses

• A. Retroviruses carry gene for RNA-dependent DNA polymerase
• B. The genetic material in mature retroviruses is RNA
• C. Retroviruses are causative agents for certain kinds of cancer in man
• D. DNA is not present at any stage in the life cycle of retroviruses.

Answer 1

Answer: (D)

DNA is not present at any stage in the life cycle of retroviruses.

Answer 2

Retroviruses are a class of animal viruses characterized by a single-stranded RNA as their genetic material. They follow a unique replication process involving a DNA intermediate. These retroviruses carry two copies of single-stranded RNA molecules.The retrovirus life cycle begins with the reverse transcription of the RNA genome into double-stranded DNA. This newly formed DNA is then integrated into the host genome. Inside the cell's cytosol, the single-stranded RNA genome undergoes reverse transcription into double-stranded DNA, facilitated by an enzyme called reverse transcriptase. This enzyme, which acts as an RNA-dependent DNA polymerase, uses RNA as a template to synthesize DNA. Additionally, it possesses RNase H activity, which is responsible for degrading the RNA portion of the RNA-DNA hybrid. Native tRNA molecules serve as primers for reverse transcriptase. Once DNA synthesis is completed, the double-stranded DNA is integrated into the host genome. Retroviruses such as HIV are known to be associated with the development of diseases, including certain cancers like leukemia (specifically, HIV-1 is implicated in this context).