Exam LSAT Section 1 Logical Reasoning topic 1 question 260 discussion

Actual exam question from Test Prep's LSAT Section 1 Logical Reasoning

Question #: 260
Topic #: 1

[All LSAT Section 1 Logical Reasoning Questions]

Some types of organisms originated through endosymbiosis, the engulfing of one organism by another so that a part of the former becomes a functioning part of the latter. An unusual nucteomorph, a structure that contains DNA and resembles a cell nucleus, has been discovered within a plant known as a chlorarachniophyte. Two versions of a particular gene have been found in the DNA of this nucleomorph, and one would expect to find only a single version of this gene if the nucleomorph were not the remains of an engulfed organism's nucleus.
Which one of the following is most strongly supported by the information above?

A. Only organisms of types that originated through endosymbiosis contain nucleomorphs.
B. A nucleomorph within the chlorarachniophyte holds all of the genetic material of some other organism.
C. Nucleomorphs originated when an organism endosymbiotically engulfed a chtorarachniophyte.
D. Two organisms will not undergo endosymbiosisunless at least one of them contains a nucleomorph.
E. Chlorarachniophytes emerged as the result of two organisms having undergone endosymbiosis.

Show Suggested Answer

Suggested Answer: E 🗳️
This next Inference question involves a scientifically challenging argument. But buried amidst the technical terms is some fairly straightforward formal logic, so hopefully you didnt let yourself get bogged down in the terminology. Endo (no reason not to shorten this) is a process by which one organism engulfs another and the engulfed organism becomes a functioning part of the whole. Something strange that looks like a cell nucleus (lets shorten its cumber somename to nuc) has been found inside a plant (chlor); can you see where this is going? Perhaps endosymbiosis occurred here? What follows requires some interpretation (and thats, after all, what Inference questions are all aboutinterpretingand combining): If the nuc was NOT originally part of an organism that got engulfed, then wed expect one version of a particular gene in its DNA. Thats a simple formal logic statement, albeit one with complicated terms. Nonetheless, the contrapositive applies: If theres NOT one version of the gene, then the nuc WAS part of something that got engulfed. And were told, in fact, that there are TWO versions of the gene, so we know for sure that engulfing took place. As E. puts it, chlor was formed as a result of endo.

by [deleted] at March 9, 2025, 1:37 p.m.

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