Tiernan O'Halloran of Connacht is also included as are John Cooney and Nevin Spence, amongst others, from last year's Irish squad.
Ireland open their campaign with a fixture against Italy on Friday, February 5 and will again make Dubarry Park in Athlone their home for the tournament.
Commenting on his selection, Clarke said: "The attitude of the players has been excellent, both in their individual attention and motivation while developing with their provincial rugby and fitness coaches and while playing for their clubs.
"The warm-up games against the provincial development sides have provided the opportunity to develop our game and identify the areas we need to improve.
"We all recognise the potential of the squad while respecting the challenges ahead, the first of which is to start the Six Nations campaign against Italy at home with a good performance.
"Being the first game of the championship means we have little knowledge of the opposition, so our concentration is to be accurate with and without the ball."
IRELAND UNDER-20 Squad (2010 RBS U-20 6 Nations Championship):
Backs (12) -
Andrew Conway (Blackrock College RFC/Leinster)
John Cooney (UCD/Leinster)*
Eoin Griffin (Corinthians/Connacht)
Michael Heaney (Belfast Harlequins/Ulster)
Darren Hudson (St. Mary's College RFC/Leinster)
Brian Kingston (Blackrock College RFC/Leinster)
Brendan Macken (Blackrock College RFC/Leinster)
James McKinney (Queen's University/Ulster)
David McSharry (UCD/Leinster)
Tiernan O'Halloran (Galwegians/Connacht)
Forwards (14) -
Niall Annett (Belfast Harlequins/Ulster)
Denis Buckley (Corinthians/Connacht)
Patrick Butler (Shannon/Munster)
Bryan Cagney (UCC/Munster)
David Doyle (UCD/Leinster)
Brian Hayes (Cork Constitution/Munster)*
Stewart Maguire (Old Belvedere/Leinster)
Ben Marshall (UCD/Leinster)
Jordi Murphy (Blackrock College RFC/Leinster)
Robin O'Sullivan (Bective Rangers/Leinster)
David O'Callaghan (UCC/Munster)*
Jack O'Connell (Lansdowne/Leinster)*
Rhys Ruddock (UCD/Leinster)*
Dominic Ryan (Lansdowne/Leinster)*
* Denotes previously capped player at Under-20 level