"Discuss the role of point mutations and duplications in the evolution of a protein family of your choice."This does not mean:
"Write everything you know about point mutations and duplications and occasionally mention a protein family as an example when you can."If you are not discussing the evolution of your protein family - or explicitly providing background material - you are not answering the question.
As a marker, I do not enjoy giving out bad marks. It is especially frustrating if the answer is long and most of what was written is right. Marks cannot be given for just being right, though. Otherwise, people could just write about whatever they wanted in an exam, which would defy the point somewhat.
The same advice applies to diagrams/figures. Don't just reproduce a figure from a lecture because it relates in some undefined way to the topic being examined. Draw a figure to illustrate a specific point. Better still, customise a figure from a lecture - or even create a totally new figure yourself - to illustrate a specific point. Then draw attention to that point by citing the figure at the appropriate point in the text. Don't just hope that I, as a marker, will make the right connection. Of course, I know how the figure connects to the topic/question - I set the question! I want to see whether you know! Unfortunately, unless given evidence to the contrary, I will have to assume that you do not.
Finally, please re-read your answer at make sure that, at the very least, sentences make sense. Exams are your opportunity to demonstrate what you know. Returning garbled nonsense is not a good way to do this. (Unless, of course, garbled nonsense is an accurate representation of what you know, in which case you have other problems!)