Tranmere’s Charlie Barnett had the first shot on goal as his effort from 18 yards had to be blocked away by Sean O’Hanlon for a corner which came to nothing.
Dons striker Sam Baldock was looking lively and it took some good defending from Antony Kay and former Dons stopper Ben Chorley to prevent him from bagging his 10th of the season.
The home team came flying out of the blocks in the second period and the Tranmere defence had to be alert to block shots from Jason Puncheon and Luke Chadwick.
But they did not have it all their own way as Aaron Cresswell found space to get a shot away but it flew over Price’s crossbar.
Roberto Di Matteo then brought on Gallen in place of Ali Gerba and the substitution proved to be inspired as the veteran hitman scored almost instantaneously from Puncheon’s corner to seal the points.