Q.18 The type of nucleic acid present in λ-phage is
(A) Double stranded DNA
(B) Single stranded circular DNA
(C) Single stranded DNA
(D) Single stranded RNA
Lambda phage contains double-stranded DNA as its genetic material. This makes option (A) the correct choice in the multiple-choice question. Understanding its genome helps in studying bacteriophage biology and molecular genetics.
Correct Answer
The type of nucleic acid in λ-phage (lambda phage) is double-stranded DNA. Lambda phage, a temperate bacteriophage infecting E. coli, has a linear double-stranded DNA genome approximately 48.5 kilobase pairs long. This DNA enables both lytic and lysogenic cycles, key to its research significance in genetics.
Option Analysis
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(A) Double stranded DNA: Correct, as confirmed by structural studies showing λ-phage’s icosahedral head packed with ~48.5 kbp dsDNA.
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(B) Single stranded circular DNA: Incorrect; this describes phages like φX174 or M13, not λ-phage, which has linear dsDNA.
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(C) Single stranded DNA: Incorrect; ssDNA occurs in some phages (e.g., M13), but λ-phage uses dsDNA for stability and replication.
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(D) Single stranded RNA: Incorrect; RNA phages like MS2 or Qβ have ssRNA, whereas λ-phage is a DNA virus.
