Q.38 Match the virus in Group I with the type of genome it contains in Group II.
Group I                                                  Group II
P. T4 bacteriophage                            1. dsRNA
Q. SARS–CoV–2                                    2. ssDNA
R. Pseudomonas phage Φ6               3. dsDNA
S. ΦX174 bacteriophage                    4. ssRNA
(A) P–3, Q–4, R–1, S–2
(B) P–2, Q–1, R–4, S–3
(C) P–4, Q–3, R–2, S–1
(D) P–1, Q–4, R–2, S–3

Correct Answer: (A) P-3, Q-4, R-1, S-2

T4 bacteriophage contains dsDNA, SARS-CoV-2 has ssRNA (+sense), Pseudomonas phage Φ6 features dsRNA, and ΦX174 bacteriophage possesses ssDNA.​

Genome Types Explained

T4 bacteriophage (P) belongs to dsDNA viruses (Group I of Baltimore classification), with a large linear double-stranded DNA genome (~169 kb) that infects E. coli. SARS-CoV-2 (Q), a positive-sense ssRNA virus, has a ~30 kb single-stranded RNA genome enabling direct translation upon infection. Pseudomonas phage Φ6 (R) is a unique dsRNA virus with a segmented genome (L, M, S segments) packaged in a lipid envelope. ΦX174 (S) is the classic ssDNA virus, circular and ~5.4 kb, replicating via a double-stranded intermediate.​

Option Analysis

• (A) P-3, Q-4, R-1, S-2: Matches perfectly—dsDNA (T4), ssRNA (SARS-CoV-2), dsRNA (Φ6), ssDNA (ΦX174).​

• (B) P-2, Q-1, R-4, S-3: Incorrect; T4 lacks ssDNA (it’s dsDNA), SARS-CoV-2 is not dsRNA.​

• (C) P-4, Q-3, R-2, S-1: Wrong; T4 has no ssRNA (dsDNA instead), Φ6 lacks ssDNA (dsRNA).​

• (D) P-1, Q-4, R-2, S-3: Fails; T4 is not dsRNA (dsDNA), Φ6 not ssDNA.​

Introduction to Virus Genome Matching

T4 bacteriophage SARS-CoV-2 Pseudomonas phage Φ6 ΦX174 genome types form a classic question in virology for exams like GATE Biotechnology and IIT JAM. Understanding dsDNA, ssRNA, dsRNA, and ssDNA classifications aids in matching Group I viruses to Group II genome types accurately.​

Virus Genome Characteristics

• T4 Bacteriophage: Large dsDNA genome (~169 kb, linear), infects E. coli, used in molecular biology.​

• SARS-CoV-2: Positive-sense ssRNA (~30 kb), causes COVID-19, replicates via RNA-dependent RNA polymerase.​

• Pseudomonas Phage Φ6: Segmented dsRNA (12 kb total), first enveloped dsRNA phage, infects Pseudomonas syringae.​

• ΦX174 Bacteriophage: Circular ssDNA (~5.4 kb), smallest DNA virus, first fully sequenced genome.​

Exam Question Breakdown

This matching tests Baltimore classification knowledge. Option (A) correctly pairs P-3 (dsDNA), Q-4 (ssRNA), R-1 (dsRNA), S-2 (ssDNA), aligning with standard virology facts.​