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GATE 2019 BT Q.9: solution and answer

GATE 2019 · BTQ.9 · 1 mark · MCQ

Which of the following processes can increase genetic diversity of bacteria in nature?
P. Conjugation
Q. Transformation
R. Transduction
S. Transfection

  1. (A)

    P only

  2. (B)

    P and Q only

  3. (C)

    P, Q and R only

  4. (D)

    P, Q, R and S

See the question in the paper
GATE 2019 BT question 9Tap to open full size

Answer and solution

ANSWER

The correct answer is (C) P, Q and R only.

Official answer: C or BSource: Official answer key, GATE 2019 BT (IIT Madras)

  1. P. Conjugation: direct cell-to-cell transfer of plasmid/chromosomal DNA through a pilus. This occurs naturally among bacteria in the environment (e.g., spread of antibiotic-resistance plasmids) and increases genetic diversity. Include.

  2. Q. Transformation: uptake of free (naked) DNA released from lysed cells by naturally competent bacteria such as Streptococcus pneumoniae, Bacillus subtilis and Neisseria species. This is a spontaneous natural process and increases genetic diversity. Include.

  3. R. Transduction: bacteriophages package host bacterial DNA (generalized transduction) or adjacent genes (specialized transduction) and inject it into a new host cell during their normal infection cycle in nature. This increases genetic diversity. Include.

  4. S. Transfection: the deliberate, artificial introduction of naked DNA or viral nucleic acid into cells using laboratory methods (chemical reagents, electroporation, etc.). It is a technique performed by experimenters, not a process bacteria undergo spontaneously in nature. Exclude.

  5. Since only conjugation, transformation and transduction are natural mechanisms that increase genetic diversity of bacteria in nature, the correct option is (C) P, Q and R only.

KEY IDEA

Bacteria acquire new genetic material through three natural horizontal gene transfer mechanisms — conjugation (direct transfer via pilus), transformation (uptake of free environmental DNA), and transduction (phage-mediated DNA transfer). Transfection is a laboratory technique for artificially introducing nucleic acid into cells and is not a process that occurs on its own in nature.

WATCH OUT FOR

Confusing transfection (lab-mediated artificial introduction of naked DNA/RNA into cells) with transformation (natural uptake of free DNA by competent bacteria) — both involve "naked" nucleic acid entering a cell, but only transformation is a process bacteria undergo spontaneously in nature.

From the GATE 2019 BT paper. Every question of this paper · Download the full paper · All 2 Microbial genetics questions, with notes