This is 18-year-old Turnbull's first-ever international call-up, and comes at the end of a season in which the centre-half has impressed for Saints' Under-21 side.
Chambers, meanwhile, has been a regular for England at under-19 level since making his debut for Noel Blake's side last September.
The Elite Round games determine which countries qualify for the 2013 UEFA European Under-19 Championship, which takes place in Lithuania in July and August.
Having progressed through the Qualifying Round last autumn, England have been drawn into Elite Round Group 6 along with Scotland, Belgium and Georgia.
The four teams will face each-other once, with the team that finishes top of the group qualifying for this summer's finals.
Belgium have been designated as the hosts for Group 6 fixtures, with England's first game seeing them take on Georgia at 6pm on Friday 24th May at the Breevenstadion in Bornem.
Then, two days later, the Young Lions face Belgium at 7pm at De Leunen in Geel, before rounding off their Elite Round games against Scotland on Wednesday 29th May (6pm) at KFC Oosterzonen in Westerlo.