McDonald, who agrees a short-term deal with the club until January, arrives after leaving Championship outfit Birmingham City whilst Pattison signs on a season-long loan from Middlesbrough.
Aged 21 and 20 respectively the duo arrive in Somerset for their first taste of EFL action and are both available for Saturday’s season opener at Bury subject to clearance.
Having risen through the Academy ranks at Crystal Palace and Fulham, McDonald swapped London for the Midlands at the of 16 and the decision was soon vindicated by netting 10 times in the 2016/17 campaign for the Development Squad at St Andrews.
Able to operate on the wing or further forward, the 21-year-old spent time on loan at Vanarama National League side Solihull Moors last season and will now make the step up to League Two.
Following a similar path, Darlington-born Pattison was signed by Boro at the age of nine and became a regular for both the under-18s and under-23s.
Impressing throughout the age groups the 20-year-old, progression was paused by an injury early last season before an initial one-month loan move to York City in December.
Making the transition to senior football appear easy, Pattison extended his stay with the Minstermen for the remainder of the campaign after claiming the Press Player of the Month award for December.
During their time at Huish Park, Alex will wear number 17 with Wes claiming the number 21 jersey.