Up , charm and top quarks have a charge of + , while down , strange and bottom quarks have a charge of - .
Quarks have fractional electric charge valuesâ '' either â ' or + times the elementary charge , depending on flavor . Up , charm , and top quarks ( collectively referred to as up-type quarks ) have a charge of + , while down , strange , and bottom quarks ( down-type quarks ) have â ' .