"Does the rule extend to paranthesis? It should, because it ... of paranthesis is to interrupt the flow of the sentence."
"The rules about parentheses and ending punctuation are not quite the same as either system for quotation marks and ending punctuation."
Actually, the rules are about the same, or at least analogous:
In either the US or the UK style, enclose within parentheses only what you want to parenthesize.
The gender of the noun is the same (male).
(The gender of the noun is the same.)
A special consideration is a complete sentence parenthesized within another complete sentence. The parenthesized sentence doesn't begin with a capital letter unless it begins with a word that's normally capitalized, like "I" and it doesn't have an ending period. However, it may have an ending question mark or exclamation mark.
The gender (gender is not the same as sex) is unknown. The gender (is gender the same as sex?) is unknown. The gender (I mean gender, not sex!) is unknown.
"I don't have time at the moment to write out the rules I know, but I'm sure you'll find them in the "writing guides" at Intro B. For example: http://ccc.commnet.edu/grammar/marks/parentheses.htm"
That source seems to cover the points I've made, except that it could be more explicit about a closing parenthesis at the end of a sentence. That is, write
The gender is the same (male).
Not
* The gender is the same (male.)
There might be a temptation to make that error because of confusion with the US rule for putting periods within quotes at the end of a sentence whether it makes sense or not.
Good style (UK):
Mark the package "fragile".
Absurd style (US norm):
Mark the package "fragile."