How is the comedy in act one of Much Ado About Nothing constructed? Also, what serious elements are emerging and how are they presented to us dramatically?

The comedy in Much Ado About nothing is mainly constructed from the word play between Benedick and Beatrice. The first time this happens is line 108 in scene one of the first act, where Beatrice starts an argument. Almost all of the comedy in the play (and definitely all in act one) is constructed in this way with the arguments between the two intriguingly "sharp tongued" characters. This is the only comedy to be found in act one which is mainly devoted to introducing the characters, their traits and their motivations.

An example of a serious element in this supposed comedy is that some of the male characters (Don Pedro, Claudio, Benedick, Balthasar and Don John, to be precise) have just returned from war. This is only touched upon very briefly right at the very begining of Act 1 with Leonato asking a messenger questions about it, but none the less, war is definitely no laughing matter.

Another example of a serious element is Don John being evil and saying to his followers (in line 25 of Act 1, Scene 3) that the would rather be a "canker in a hedge than a rose on his grace". A "canker" is a disease that plants get, so what Don John is saying is that he'd rather make a hedge ill than make "his grace"(god?) smell like roses. This and all of Don John's other lines in the first paragraph are said in blank verse, as opposed to the lines of his brother, Don Pedro, who speaks in verse ( most of the time iambic pentameter). This could be used to imply that he is a villain (although he admits this himself) or that he is talking about bad things. Either way, he is definitely serious.