Hibernian defender Porteous joined up with the full squad earlier this week after Clarke’s side were hit by a raft of late call-offs ahead of their final Euro 2020 qualifiers with Cyprus and Kazakhstan.
But Gemmill - whose team take on Greece at Tynecastle on Friday night in their latest European Championship qualifier - believes the graft being put in by the rest of his youngsters this week is a sign they are determined to make their own step up to the senior team.
Scotland Under-21s could move clear at the top of Group 4 with a win in Gorgie and Gemmill told the Scottish FA website: “These players are learning as they go but at the same time have crucially formed an identity.
“They have a work ethic that gives them all the maximum chance to improve further towards their ambition to play for the Scotland national team.
“The fact we have conceded just one goal in our four games is a foundation the players can build on.
“For me as manager it also shows me that the players have the ability to gel as a group.”
“That can be a challenge at international level compared to club level, where you work together every day, but the players are showing me they are capable of this and are learning with each passing international break.”