When you are comparing a genome of two different isolates by small piece-by-small piece to find differences, this is known as _________ analysis.

• A. Kmer based analysis
• B. hqSNP analysis
• C. wgMLST analysis
• D. PCA analysis

Answer: (A)

Breaking genomes into short substrings and comparing those pieces across isolates is k-mer based analysis. By choosing a word length k (for example, 31), you generate all k-mers from each genome and compare their presence, absence, and frequency between the two genomes. This alignment-free approach quickly reveals how similar or different the isolates are, capturing SNPs, small indels, and content differences reflected in the k-mer sets. It’s fast and robust to rearrangements and divergent regions because it doesn’t rely on aligning the entire genome.

High-quality SNP analysis, in contrast, relies on mapping reads to a reference genome and calling single-nucleotide changes, focusing on nucleotide differences at mapped positions rather than comparing fragment sets across the whole genome. wgMLST uses predefined genes and their allelic variants, not a genome-wide fragment-by-fragment comparison. PCA is a statistical method used to visualize relationships by reducing data dimensions, not a specific method for genome comparison.