I think you're talking about how the gmail web interface threads emails of the same subject together. If you use the Mail app on the iPhone then no, you cannot do this. If you need this functionality you could always bring up gmail in safari.
i have sevrtal times the the prob with diffrent stuff. so i have written first for me a independ group mail software for the iPhone. it is still now also on the iTunes Store. you can create email groups and add email adresses and more...