Q24

[hyewonkim89]

I was down to (D) and (E) and ended up picking (D).

I'm still having a hard time eliminating (D) completely.

Please help!

[tommywallach]

Hey Hye,

This one is actually more straightforward, as it's based really deeply in the text as written (We don't need to do much inferring). Let's go through the answers:

(A) CORRECT. The passage discusses frogs, then immediately after says: "...in human and other mammalian embryos, polarity develops much later, as many stages of cell division occur with no apparent asymmetries among cells." In other words, polarity comes much later.

(B) This is contradicted by the sentence just cited.

(C) P-granules are not said to exist in humans.

(D) The passage says, "A similar sperm-driven mechanism is also thought to establish body orientation in some comparatively simple vertebrates...though apparently not in more complex vertebrates such as mammals." This means humans are NOT using the sperm-driven mechanism.

(E) The sentence I quote in (D) also contradicts this one. Humans are more complex than simple vertebrates.

Hope that helps!

-t

[hyewonkim89]

Hi Tommy,

I think you accidentally put an explanation for #23.

Please help me on #24!

Thank you!

Hye-Won

[tommywallach]

Hey Hye,

Silly me! Let's try this again!

So you should always be happy when they say what does "blah blah blah" mean in the passage. The answer will always be very literal:

"There is an astonishing conservation of mechanism in this process: the genes that help make eyes in flies are similar to the genes that make eyes in mice or humans."

So the point is that it's cool how the same genes do the same thing in different species.

(A) Not about different parts. The example is just eyes.

(B) Nothing about genetic material being wasted in the passage.

(C) We don't hear about the number of genes involved.

(D) Flies and mice are not particularly different in terms of complexity (mice are bigger, but flies can fly and stuff). Plus, the passage doesn't really focus in on the fact that there is a gradient of complexity, only that the species are different.

(E) CORRECT. Eyes (analogous structures) in different species (humans, mice, flies) are brought about by similar genetic means.

Hope that helps!

-t