195. Which regions of the genome are best suited for generating DNA Barcodes for species
identification?
A. Organellar genes
B. Ribosomal genes
C. Histone genes
D. Non coding regions of the genome

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Explanation:

DNA barcoding is a technique used to identify species by analyzing a short, standardized region of the genome. The success of this method relies on selecting DNA regions that are:

• Conserved within a species

• Variable between species

• Easily amplified by universal primers

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Why Organellar Genes?

Organellar genes, particularly those from the mitochondrial genome (in animals) and chloroplast genome (in plants), are ideal for DNA barcoding due to several key features:

• High mutation rate: Especially in mitochondrial DNA (mtDNA), enabling species-level resolution.

• Maternal inheritance: Reduces recombination, preserving species-specific signatures.

• High copy number: Easier amplification even from degraded samples.

• Universally present: Most eukaryotic organisms possess mitochondria or chloroplasts.

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Common Barcode Genes:

• COI (cytochrome c oxidase I) — widely used in animals.

• rbcL and matK — standard barcodes for plants (from chloroplast DNA).

• ITS (Internal Transcribed Spacer) — sometimes used in fungi and plants, though this is nuclear.

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 Why Not Others?

• Ribosomal genes: Often too conserved or repetitive.

• Histone genes: Highly conserved, offering little variability.

• Non-coding regions: Often lack reliable primers and may not be universally present or easily amplifiable.