'which make up' is correct and usable in written English.
You can use this phrase when referring to a group of items that form a whole. Example: I collected all of the pieces, which make up the puzzle.
Developing countries, which make up the bulk of W.T.O.
Names the 3 tongs which make up the Chinese Mafia.
The facility consists of six individual wineries, which make up the overall vineyard.
In 2009, CashCall added mortgages, which make up the bulk of the company's business.
The BJP's base is among upper castes, which make up about a fifth of UP's population.
The same day, Enron shut its trading operations, which make up the majority of its business.
These are places where short strings of the chemical "letters" which make up DNA are repeated.
These are picture elements, like the dots which make up a picture on a television screen.
Second, the departments responsible for the public services, which make up around 55% of the total.
Describes the problems created by reruns, which make up the July and August programs.
The three medieval streets which make up the centre are already choked with cars.
