Q. Consider the following statements:

1. Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes.
2. Common cold is sometimes caused by an adenovirus whereas AIDS is caused by a retrovirus.

Which of the statements given above is/are correct?

• 1 only
• 2 only
• Both 1 and 2
• Neither 1 nor 2

Answer: (b) 2 only

Adenoviruses:

• ​Adenoviruses are a group of common viruses that infect the lining of your eyes, airways and lungs, intestines, urinary tract, and nervous system. They’re common causes of fever, coughs, sore throats, diarrhoea, and pink eye. Infections happen in children more often than in adults, but anyone can get them. 
• Adenovirus is a type of virus that has no envelope whereas retroviruses are characterized as enveloped viruses.
• Scientists use these viruses as “Viral Vectors” in making vaccines. Viral vectors are tools used to deliver genetic material into cells.
• Adenoviruses have double-stranded DNA genomes while Retroviruses have single-stranded DNA genomes. 
• Common cold can sometimes be caused by adenoviruses while AIDS is caused by a retrovirus.
  • HIV is classified as a retrovirus because it contains reverse transcriptase. It is a D-type virus in the Lentivirus family.   

Retrovirus

• Retroviruses are a type of virus in the viral family called Retroviridae. A retrovirus uses RNA as its genomic material.
• A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell.
  • After invading a host cell’s cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backwards).
  • The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus.
  • The host cell then treats the viral DNA as part of its own genome, transcribing and translating the viral genes along with the cell’s own genes, producing the proteins required to assemble new copies of the virus.
• Many retroviruses cause serious diseases in humans, other mammals, and birds.