Fetch genomic region(s) from refseq genomes

Question

[usr2]

I would like to fetch specified genomic regions from refseq genomes without having to download the full genome. The regions are previously identified with a hmmer search. To my understandment Ensembl does not have all Refseq genomes. Many thanks, D

[Pierre Lindenbaum]

give us some examples of input.

Answer 1

[GenoMax]

Using EntrezDirect.

One thing to be aware of : If you use a top level RefSeq accession for bacterial genomes there may be multiple plasmids etc in that accession. Sequences may be retrieved from those as well. You may need to eliminate some of those sequences (example below).

$ esearch -db assembly -query GCF_017165115 | elink -target nuccore | efetch -format fasta -seq_start 20000 -seq_stop 20050
>NZ_CP062740.1:20000-20050 Escherichia coli O157:H7 strain Z1723 plasmid pZ1723-1, complete sequence
CATCCGCTTGCAGCACACCGCTGAAGCAGGCAAGATGAGTCTGCGGATGGA
>NZ_CP062739.1:20000-20050 Escherichia coli O157:H7 strain Z1723 chromosome, complete genome
ACATACATTAAGCCTTAATTTTCCTCTGACAACGGTCAGTGCAGCAAACAA
>CP062740.1:20000-20050 Escherichia coli O157:H7 strain Z1723 plasmid pZ1723-1, complete sequence
CATCCGCTTGCAGCACACCGCTGAAGCAGGCAAGATGAGTCTGCGGATGGA

Answer 2

[barslmn]

samtools can retrieve sequences without downloading the full genome.

eg.

samtools faidx https://igv.genepattern.org/genomes/seq/hg19/hg19.fasta chr21:10,000,000-10,000,020