It is proposed to introduce mosquitoes into the wild with genetic alterations that destroy their disease-carrying capacity. ██ ████ ███ ███ █████████ ████ ██████████ █████ ██████████ ██ ████████ ██ █ ████████ ███ ███████ ███████ ████ ███ ███████ ████████████████████ ██████ ██ █████████ ███ █████████ ████ █████ █████████ ████ ███ █████████████ ███████ ██████ ███████ █████ █████ ███ ███████████ ██ █ ███████ ████████ ██████ ███ █████ ██ █████ ██ █████ ██ ████████████ ███████ █████ ███████ ███ █████████ ██ ███ ████████████ ███ ██████████ ██ ████████ ██ ████ ██ █████ ███ ██████ ████████████ ███ ████████
The proposal promises to deliver on two goals: replace the dangerous wild mosquito population with a harmless engineered one, and leave no room for another disease-transmitting strain to flourish. To those ends, it offers three candidates. The stem's prompting to "identify a discrepancy in the proposal" gives us an up-front reason to assess those candidates against the proposal's goals as we read.
The first gene would interfere with the mosquitoes' ability to find mates, but a mosquito that can't find mates can't reproduce. This gene would just produce a bunch of mosquitoes that die without offspring. No hope of replacing the wild population there.
The second gene is fine: destroying the disease parasite leaves the mosquito itself alive and healthy enough to reproduce – that's exactly what we need to replace the wild population with our mutants
The third gene suffers from a similar problem as the first. It just makes mosquitoes that die more, which doesn't bode well for the goal of replacing the wild population.
If you're focused on finding the discrepancy from the jump, identifying it is quite doable. The key is to form a precise understanding of the proposal's stated goals.
Which one of the following ██████████ █ ███████████ ██ ███ ████████ ██████
It is presupposed ████ ███ █████ █████ █████ █████ ███████ ████ ██ ███████ ███ ██████ ████ ███ █████ ██ ███ ███████████
Equally easy is very strong wording, and for (A) to be correct, the idea that these genes are equally easy to [use] needs to find support in the stimulus. Almost like an MSS question, we need to ask ourselves "where in the stimulus does it presuppose that all three genes would be equally easy to isolate and insert?" (A) is wrong because that concept is absent in the stimulus.
Two of the ████████ ████ ██ ██████████ ████████████████ ████████ ██ ███ ████ ████████ ██████████ █████ ██████████ ███ ████ ██ ███ █████████
Two of the proposed genes — the no-mating gene and the die-a-lot gene — would prevent the engineered mosquitoes from reproducing, which directly jeopardizes the goal of replacing the wild population. The parasite-destruction gene doesn't have this problem.
It does not ████ ████ ███████ ████████ █████ ████ ██████████ ████ ██ ███ ████████████ ████ ██ ████████ ██ ███ ██████ ██████ ██ ████ ███ █████
Like (D), (C) would be relevant to a different conclusion than the one the stimulus actually makes. The conclusion (C) imagines is something like "mosquitoes are bad and should be eliminated." But our actual conclusion is that these genes could replace the wild mosquito population. That's a much narrower claim.
(C) underscores a common theme when evaluating LSAT arguments: nail down the argument's precise conclusion, and don't stray from its scope.
None of the █████ ████████ ████████████ █████ ██████ ████ █████ █████ ██ █████ ██████████ ██ ███ █████ █████
Like (C), (D) would be relevant to a different conclusion than the one the stimulus actually makes – it assumes the proposal's goal is to reduce the mosquito population in a given area. But our actual conclusion is that these genes could replace the wild mosquito population.
(D) underscores a common theme when evaluating LSAT arguments: nail down the argument's precise conclusion, and don't stray from its scope.
Evidence is not █████████ ██ ████ ████ ████ ███████████ ██████ ███ ████ ████████████ ██████ ██ █ ███████ ██████
(E)'s version of wrongness is common in flaw questions: "the argument is flawed because it doesn't provide evidence for [one or more of its premises]." The thing about premises, though, is that they're the starting points of the argument. You don't get to demand evidence for premises – premises are given.
The stimulus establishes that each of these genes would in fact do the thing it's supposed to do (i.e. stop mating, kill parasites, or kill mosquitos). We don't need testing to believe those claims – they're simply asserted as premises.
Identifying a flaw in an argument's reasoning means showing that the conclusion doesn't follow from the premises — not that the premises themselves are unverified.