DNA sequencing is becoming both faster and cheaper. Now, it is also becoming tinier.

A British company said on Friday that by the end of the year it would begin selling a disposable gene sequencing device that is the size of a USB memory stick and plugs into a laptop computer to deliver its results.

The device, expected to cost less than $900, could allow small sequencing jobs to be done by researchers who cannot afford the $50,000 to $750,000 needed to buy a sequencing machine.

It might also help doctors to sequence genes at a patient’s bedside, wildlife biologists to study genes in the field, or food inspectors to identify pathogens.

“You don’t need to buy instruments,” Clive G. Brown, the chief technology officer of the company, Oxford Nanopore Technologies, said in an interview. “It’s pay-as-you-go sequencing.”