Grammar Tip: AND

Retain "and" before the last item in a series, even though that last item consists of two words joined by "and": We need to increase our expense budgets for advertising, staff training, and research and developent.
(NOT: We need to increase our expense budgets for advertising, staff training, research and development.) (research and development = R&D = expressão composta por duas palavras unidas por "and")
Note: Never use "and" before "etc."
Source: YourProofreadNow