When casting a spell, do you add your Dexterity/Strength modifier to attack and damage?

@JeremyECrawford when casting a spell, do you add your Dex/Str mod to attack and damage?

— SargentFamily (@SargentFamily) February 4, 2016

You use your spellcasting ability modifier when you make an attack roll with a spell (PH, 194 & 205). #DnD https://t.co/xycM0Tfil9

— Jeremy Crawford (@JeremyECrawford) February 4, 2016