'Just as' incorporates time. 'I noticed Anna walk through the door just as Mary left the room.' Mendel did not discover the genes at the same time as atoms are to understanding of architecture of universe. The sentence becomes nonsensical.

Thanks.

"Just as" seems a better answer to me, as I never thought of "what" can be used to compare 2 expressions.

hanspaul wrote:Quoted from e-gmat.com

Father of modern genetics, Gregor Mendel discovered genes that are to understanding to complex structure of human body ______ atoms are to understanding of architecture of universe.


A : Just As
B : What

I chose "A" but answer is "B". Anyone can explain why "just as" is not correct?

kal750gmat wrote:'Just as' incorporates time. 'I noticed Anna walk through the door just as Mary left the room.' Mendel did not discover the genes at the same time as atoms are to understanding of architecture of universe. The sentence becomes nonsensical.

I do not believe the above explanation is accurate.

"What" is the answer only because it is the correct idiomatic answer. This is an idiom for comparison. The correct structure of the idiom is

X that is to.....what Y is to....

In this specific example, it leads to..

genes that are to .... what atoms are to ...

This also helps in preserving the parallelism of the sentence.

The correct idiom for using "Just as" is "Just as X, so Y"..

The above example could be written using this idiom as..

Just as atoms are vital to understand the architecture of universe, so genes are vital to understand the complex structure of human body..

Hope this clarifies...Feel free to let me know if any of the above is incorrect!!

Cheers!!