After Arsenal relied on late goals by Viktor Gyokeres and Dowman to snatch a 2-0 home win over Everton, second-placed Manchester City could only draw 1-1 at West Ham United a few hours later on Saturday.
The lead grew to nine points on what might prove to be a defining day in Arsenal's bid for a first English league title since 2004.
It will certainly never be forgotten by Dowman, the school kid and surely a future superstar in English soccer.
At 16 years, 73 days, he changed the game after coming on in the second half for his third Premier League appearance in a breakthrough season that has already seen him become the youngest player in Champions League history.
"He stays so calm and without fear every time he gets the ball," Gyokeres said of Dowman.
"He takes the right decision most of the time as well and with the goal, he definitely took the right one."
It was Dowman's cross from the right that was missed by Everton goalkeeper Jordan Pickford and struck the midriff of Arsenal substitute Piero Hincapie. The ball bounced across the goalmouth and Gyokeres applied the finishing touch from close range.
Then, in the seventh minute of added time, Dowman collected the ball midway in his own half after a corner was cleared, dribbled around two players, and raced clear to tap into an empty net.
City couldn't match Arsenal, surrendering the lead given to Pep Guardiola's team by Bernardo Silva in the 31st minute. Four minutes later, Konstantinos Mavropanos headed home at a corner.
The point lifts the Hammers out of the relegation zone for the first time since December and wraps up a tough week for City, who were beaten 3-0 by Real Madrid in the first leg of the Champions League's round of 16 on Wednesday.
"It's complicated ... but we have one game in hand, we have Arsenal at home - I'm not saying it will be easy to beat them - but at home I'm always positive," City boss Guardiola said.
Across London, Chelsea lost 1-0 to Newcastle United thanks to an 18th-minute goal by Anthony Gordon.
Chelsea stay fifth, but could be overtaken by Liverpool, who host struggling Tottenham on Sunday.
A 0-0 home draw with Bournemouth left next-to-last Burnley eight points from safety with just eight games remaining this season and facing an immediate return to the Championship.
The Clarets have won just four of their 30 league games.
Sunderland, another promoted team, appear to be safe from relegation but are limping towards the end of the season after a third straight home loss – this time 1-0 to Brighton & Hove Albion at the Stadium of Light.
