Like any big family, Nissan's car line always has a baby at the bottom end. Affable, affordable, and always popular, it serves the critical role of luring in lifetime customers. Sure, it's not the lavish life of an Infiniti, but it's still a life. And now Nissan has given that life to the Versa.As for the Sentra, this turn of events presented it with two choices: grow up or get out. So it embarked down the first path - a rather narrow one that involves distancing itself from its replacement while also steering clear of the Altima and Maxima just ahead. One can get lost in the shuffle when among four of a kind.But what's done is done, and for the second time in a row, the Sentra went under the knife to wake up a whole size bigger than yesterday. Nissan also retired all previous engines, removed all gears from the automatic transmission, revised several components, and redecorated every inch. A big job, yes, but Nissan had help. Together with its new spouse Renault, they felt it best that the Sentra splice its genes with a car known in France as the Renault Megane. Whatever that is.