# DBT JRF 2020 — Question 49

Exam: DBT JRF 2020 · Section: B · Topic: Molecular Biology · Difficulty: Hard

## Question

Identify the incorrect pair

## Options

- **A.** DNase I : Cleaves only double stranded DNA
- **B.** Alkaline Phosphatase : Removes 5' phosphate from the DNA
- **C.** DNA Polymerase I : Nick Translation
- **D.** RNA polymerase: Transcription

## Answer

Option A

## Explanation

Xanthomonas campestris pv. campestris is a phytopathogenic bacterium (causes black rot of brassicas). Industrially, it is cultivated for the production of xanthan gum — a high-molecular-weight anionic polysaccharide exopolysaccharide ( $\beta$ -1,4-glucan backbone with trisaccharide side chains of mannose-glucuronic acid-mannose). Xanthan gum is a food additive (E415) used as a thickener, stabiliser, and emulsifier in foods, cosmetics, and oil drilling fluids. It is NOT used as a biopesticide. Established biopesticides: Bacillus thuringiensis (Bt) — Cry toxin-producing bacterium (insecticide); Trichoderma harzianum — fungal biocontrol agent against soil pathogens; Nuclear Polyhedrosis Virus (NPV) — baculovirus used against lepidopteran pests.

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