additionally to what 小狼-san said, I would like to add, that the bit about the literal translation is a bit more tricky. As you get deeper into the japanese language, you get more accustomed to the concept of omitted subjects and objects.
So, both of your example sentences simply have omitted subjects.
Like "watashi wa chrisu desu" would USUALLY be "watashi wa watashi ga chrisu desu".
Everything before wa siply is the TOPIC of the sentence. It's not the subject. The subject simply is omitted, since it's the same as the topic. So, the LITERAL translation of "watashi wa chris desu" would be: "As for me, I am Chris."
The same is true with "genki desu ka", where anata ga simply is omitted. So the sentence would usually be "anata ga genki desu ka.", or, even more complete: "anata wa anata ga denki desu ka", so the literal translation would either be "Are you well?" or "As for you, are you well?"
Japanese just doesn't work that way, because the subjects (and objects) often are omitted. But just that they're omitted doesn't mean that they're not THERE!
So, one reason why I think that you SHOULD translate a sentence always to it's correct english (or whatever your language is) is so that you learn the true meaning of the sentence and get more aware of what exactly got omitted.
So, a dialogue like this:
A: "o-genki desu ka."
B: "genki desu."
Is just the japanese-omitting.version of:
A: "anata wa anata ga o-genki desu ka."
B: "hai. watashi ga genki desu."
All the subjects and objects are there, but just not expressed but understood. But translating that omitted version isn't the literal translation of the whole sentence. It's merely the literal translation of the abbreviated sentence.
I read in one book ("What the textbooks don't tell you" I think it was) a fine chapter about this "omitted subjects" and that newbie japanese learners often fall for the wrong(!) impression, that japanese has sentences without subjects. That's just wring. EVERY japanese sentence has it's subject, even if omitted. And that's the main part, why your translation ALSO should have it's subjects all in it's correct spot. As long as your native language isn't also in the habit of omitting subjects.