"Some of which" vs "each of which"

[PaulR952]

I have my GMAT coming up on tuesday, and I wanted to shore-up my understanding of the "some of which" vs "each of which" splits.

In this scenario "each of which" is perfectly acceptable and does not turn the second part into an independent clause:

"Roots are onion like structures with between 2 and 50 cells, each of which has toelike projections poking through the ground."

In this scenario "some of which" is wrong because it turns the second part into an independent clause:

"The nation of UAE contains 42 islands, some of which have a population of more than 500,000."

Is the issue here that each causes a subordinate clause and some can cause an independent clause? Or am I missing something with the has/have splits?

[Note: these are not GMAT or GMAT prep questions, but are based off of such because I forgot if they came from the free or purchased materials.]

Thanks!

[RonPurewal]

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