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Convert lowercase letter to N:$ sed -e '/^>/! s/[[:lower:]]/N/g' in.fasta > out.fasta #Convert #Lowercase #Fasta #N

Convert masked genome to N letters. $ perl -pe '/^[^>]/ and $_=~ s/[a-z]/N/g' genomic.fna > genomic.N-masked.fna #Genome #Masked #N #Convert

Remove N from a fasta file. Go to vi editor, type :%s/N\{25,\}//g and press enter. #Vim #vi #N #Replace #Fasta