Build Genome Index

Generate genome indexes using BWA or Bowtie2 aligners

Accepted formats: .fasta, .fa, .fna, .fasta.gz

Build Genome Index

Function:

Genome indexing is a prerequisite step for sequence alignment. It creates specialized index files from a reference genome FASTA file, enabling aligners such as BWA-MEM2 and Bowtie2 to perform rapid and efficient read mapping.

This tool supports both BWA Index and Bowtie2-build index generation.

BWA Index

Description:

BWA Index constructs Burrows-Wheeler Transform (BWT)-based index files required by BWA and BWA-MEM2 alignment algorithms.

Input:

  • Reference Genome FASTA File (*.fa, *.fasta, *.fna)
  • Output Prefix Name

Output Files:

  • .amb – Ambiguity information
  • .ann – Reference annotation
  • .bwt – Burrows-Wheeler Transform index
  • .pac – Packed sequence file
  • .sa – Suffix array

Example Output:

Ref.fa.amb
Ref.fa.ann
Ref.fa.bwt
Ref.fa.pac
Ref.fa.sa

Applications:

  • BWA-MEM alignment
  • BWA-MEM2 alignment
  • Whole Genome Sequencing (WGS)
  • Whole Exome Sequencing (WES)
  • Variant discovery pipelines

Suggested Reading:

BWA Manual

Citation:

Li, H., & Durbin, R. (2009). Fast and accurate short read alignment with Burrows-Wheeler Transform. Bioinformatics, 25(14), 1754–1760.

Bowtie2-build

Description:

bowtie2-build creates FM-index files used by the Bowtie2 aligner for ultra-fast alignment of sequencing reads against a reference genome.

Input:

  • Reference Genome FASTA File (*.fa, *.fasta, *.fna)
  • Output Prefix Name

Output Files:

  • .1.bt2
  • .2.bt2
  • .3.bt2
  • .4.bt2
  • .rev.1.bt2
  • .rev.2.bt2

Example Output:

genome.1.bt2
genome.2.bt2
genome.3.bt2
genome.4.bt2
genome.rev.1.bt2
genome.rev.2.bt2

Applications:

  • Bowtie2 Alignment
  • RNA-Seq Read Mapping
  • Metagenomics Analysis
  • ChIP-Seq Analysis
  • Transcriptomics Pipelines

Suggested Reading:

Bowtie2 Manual

Citation:

Langmead, B., & Salzberg, S. (2012). Fast gapped-read alignment with Bowtie 2. Nature Methods, 9(4), 357–359.

Important Notes:

  • Reference genome must be in FASTA format.
  • Indexing is required before alignment.
  • Large genomes may take several minutes to index.
  • Generated index files should be preserved for reuse.
  • Use the same reference genome for indexing and alignment.