Hi, there. I'm happy to help with this.

Astronomers have theorized that the Big Bang governs the behavior of interstellar dust, particles that comprise the atoms and molecules created in the progenitive explosion and persisting in even the emptiest regions of space.

First of all, the word "and" does not connect coordinating or subordinate clauses --- those require both a noun and verb. The word "and" connects two participial phrases (= participle form of a verb + object).

The compound noun, "atoms and molecules" is modified by the two participial phrases. Which "atoms and molecules"? The "atoms and molecules" that were "created" and are "persisting".

If you think about it, the phrase "the atoms and molecules created in the progenitive explosion" is not a clause because it can't stand alone as a complete sentence. That's because instead of a full verb, you merely have the participle "created."

This is why the proper parallel element is another participle --- "persisting" (in the present tense, because that's still happening, whereas the "created" happened in the past --- in fact, way back at the Big Bang!)

So, the crucial "and" connects
(a) the atoms and molecules created in the progenitive explosion,
with
(b) [the atoms and molecules] persisting in even the emptiest regions of space.

These are the two parallel participial phrases. As is often the case, the subject "the atoms and molecules" is implied and so it would be redundant to repeat it in the second phrases.

Does all of this make sense?

Only somewhat related, here's a free video lesson on GMAT SC that you may find helpful.

http://gmat.magoosh.com/lessons/599-int ... correction

If you have any further questions, please do not hesitate in asking me.

Mike
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Mike McGarry
Magoosh Test Prep

created( past participle) and persisting(present participle) are parallel here
persisting not persisted is required here because they are still existing.
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