Brains are delicate things…
Since the 1970s many sociologists have been keen to keep these separate. ‘Sex’ is usually used to refer to what set of dangly/non-dangly bits you have between your legs. This is a ‘biological given’, except for some surreptitious nipping and tucking by doctors for the ‘in between’ cases, and the existence of hermaphrodites. Of course, given all the endocrine-mimickers that are making boy fish and boy ‘gators into girl fish’n’gators, the future is anyone’s bet.
Gender is about the role you ‘play’- masculine, feminine, and neither-of-the-above. The term allows for the point that different cultures organise the symbols (colours, clothing, roles in life) differently, and that notions of “gender” change.
Ursula Le Guin, The Left Hand of Darkness,
Donna Haraway, Gender for a Marxist Dictionary
Greg Egan, Distress,
Clancy Ratcliff Notes on the Sex/Gender Distinction http://culturecat.net/node/view/149