Just four 15-a-side players, including Glasgow Warriors centre Mark Bennett, with previous sevens experience, made the squad.
"We have named a talented and experienced squad of 12 players today which we believe offers the right combinations and complimenting skill sets needed to be successful in Rio," men's head coach Simon Amor said.
"It has however been a 27-player effort and recognition must go to every player involved in the programme, as well as the hard working and exceptional management team."
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Britain's men will face New Zealand, Kenya and Japan in Pool C, while the women play Brazil, Canada and Japan in Pool C.
Men's squad
Mark Bennett, Dan Bibby, Phil Burgess, Sam Cross, Alex Davis, James Davies, Ollie Lindsay Hague, Tom Mitchell (c), Dan Norton, James Rodwell, Mark Robertson, Marcus Watson.
Reserves: Luke Treharne, Ruaridh McConnochie.
Women's squad
Claire Allan, Abbie Brown, Heather Fisher, Natasha Hunt, Jasmine Joyce, Katy McLean, Alice Richardson, Emily Scarratt, Emily Scott, Danielle Waterman, Joanne Watmore, Amy Wilson-Hardy.
Reserves: Megan Jones, Kay Wilson
(Reporting by Shravanth Vijayakumar in Bengaluru, editing by Pritha Sarkar)
