$ gunzip hg38.fa.gz
$ samtools faidx hg38.fa
❯ ll
-rwxrwxrwx 1 ken ken 3.1G May 8 16:37 hg38.fa
-rwxrwxrwx 1 ken ken 19K May 8 16:38 hg38.fa.fai
samtools faidx hg38.fa chr21 > hg38.chr21.fa
samtools faidx hg38.chr21.fa
$ samtools faidx hg38.chr21.fa
$ ll
-rwxrwxrwx 1 ken ken 46M May 8 16:39 hg38.chr21.fa
-rwxrwxrwx 1 ken ken 23 May 8 16:40 hg38.chr21.fa.fai
-rwxrwxrwx 1 ken ken 3.1G May 8 16:37 hg38.fa
-rwxrwxrwx 1 ken ken 19K May 8 16:38 hg38.fa.fai
$ samtools dict hg38.chr21.fa > hg38.chr21.dict
hg38 reference
Download
https://hgdownload.soe.ucsc.edu/goldenPath/hg38/bigZips/
https://hgdownload.soe.ucsc.edu/goldenPath/hg38/bigZips/hg38.fa.gz
make index
Extract
extract chr21
make chr21 index