Researchers are to study the genetic codes of severely-ill Covid-19 patients to find out why the disease affects some people more than others.
The Edinburgh University-led programme will identify the specific genes that cause a predisposition to the disease.
It will allow the genome sequencing of up 20,000 people who have been in intensive care with Covid-19, and 15,000 who have mild symptoms.
The findings will then be used to suggest potential treatments.
Results from the study will also inform global strategic planning for possible later waves of Covid-19 and other pandemics in the future.
The human genome is made up of billions of pieces of DNA, found in nearly every cell in the body. It is the "instruction manual" for life and errors can trigger a vast range of disorders.
The UK-wide sequencing project is being led by Dr Kenneth Baillie from the University of Edinburgh, who will be working with teams from within the NHS and Genomics England.
It has secured £28m of funding and is being hailed as "a global collaboration to study genetics in critical illness".
UK Health Secretary Matt Hancock said the study was "a further major programme in the UK's fight against Covid-19".
He added: "As a nation, we are determined to harness the UK's leadership in genomics to understand its role in viral response and whether we can use this information to identify those at greatest risk and improve their treatment."
Dr Baillie said: "Our genes play a role in determining who becomes desperately sick with infections like Covid-19.
"Understanding these genes will help us to choose treatments for clinical trials."
Sir Mark Caulfield, chief scientist at Genomics England, said the study could pave the way for new targeted medicines.
He said: "For the first time in a generation we face a global viral pandemic that is life-threatening for some people, yet others have a mild infection.
"By reading the whole genome, we may able to identify variation that affects response to Covid-19 and discover new therapies that could reduce harm, save lives and even prevent future outbreaks."