# DBT JRF 2022 — Question 134

Exam: DBT JRF 2022 · Section: B · Topic: Bioinformatics › DNA Barcoding & Species Identification · Difficulty: Medium

## Question

Which regions of the genome are best suited for generating DNA Barcodes for species identification?

## Options

- **A.** Organellar genes
- **B.** Ribosomal genes
- **C.** Histone genes
- **D.** Non coding regions of the genome

## Answer

Option B

## Explanation

DNA barcoding: organellar genes are best suited: DNA barcoding uses a standardised short DNA sequence from the genome to identify species: Ideal barcode properties: • Universal primers for PCR amplification across a wide range of species • Conserved enough for primer annealing • Variable enough to distinguish closely related species Standard DNA barcodes: • Animals: COI (Cytochrome c Oxidase I, mitochondrial gene) — evolves at ~2% per million years • Plants: rbcL + matK (both chloroplast genes); ITS (nuclear ribosomal ITS) for fungi • Fungi: ITS (Internal Transcribed Spacer, ribosomal RNA gene region) Organellar genes (mitochondrial + chloroplast) are best because: • Many copies per cell → easy PCR amplification • Maternal inheritance → well-defined phylogenetic signal • Known evolution rates suitable for species-level resolution Why not histones or non-coding regions: histones evolve too slowly; non-coding regions too variable with no universal primers. Answer: Organellar genes (COI, rbcL, matK) are best for DNA barcoding due to universal primers and appropriate variability.

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