The French biologist Jean-Baptiste de Lamarck (1744-1829) outlined a

The French biologist Jean-Baptiste de Lamarck
(1744-1829) outlined a theory of evolutionary change
in 1809, 50 years before Darwin's On the Origin of
Species. Lamarck's basic idea was that organisms
(5) change in adapting to their environment and then pass
on to their offspring the new characteristics they have
acquired. Since then, Lamarck has been ridiculed for
presumably implying, for example, that giraffes
developed their long necks by stretching, generation
(10) after generation, toward the leaves of trees. Most
modem biologists are adamant that nothing of the
sort occurs, ever. But the molecular immunologist
Edward J. Steele is attempting to revive Lamarckism:
he and his colleagues claim to have found evidence
(15) for a Lamarckian hereditary mechanism in the
immune system.

The immune system is an evolutionary puzzle in
its own right: How is it that our bodies can quickly
respond to so many different kinds of attacks? Is all this
(20) information in the genes? If so, then how does our
immune system defend against new diseases? Part of
the answer comes from the fact that some immune
system cells contain genes that mutate with unusual
frequency. The most common type of mutation is a
(25) sort of genetic “typo" that occurs when a cell’s DNA
is transcribed into RNA, the molecule that helps to
assemble proteins. These mutations allow the immune
system to test our different defenses until it finds one
that does the job.

(30) Steele hypothesizes that the altered RNA then
reverts back into DNA. Indeed, such “reverse
transcription” of RNA back into DNA has been
observed frequently in other contexts. But the
troublesome question for Lamarckians is this: Could
(35) this new DNA then be carried to the reproductive
genes (in the sperm and egg cells), replace the original
DNA there, and so be passed on to an organism's
offspring? Steele and company believe this is possible,
and they have devised an elegant, but speculative,
(40) story to describe how it might happen using known
biological mechanisms. They believe a virus could
carry the altered DNA to the reproductive cells and
replace the DNA in those cells.

But even if the process Steele and his colleagues
(45) describe is possible, does it ever actually occur?
Evolutionary mechanisms are never observed directly,
so we must make do with circumstantial evidence.
Steele and his colleagues claim to have found such
evidence, namely a “signature” of past events that is
(50) “written all over” the genes that carry instructions for
immune system responses. They claim that a distinct
pattern of mutations concentrated in particular areas of
these genes “strongly suggests” that, in the past,
information has been transferred into DNA in the
(55) reproductive organs. Other biologists are not so
easily swayed. They suggest there may be other, less
radical explanations for the pattern of mutations that
Steele cites.

1. Which one of the following most accurately states the main point of the passage?

(A) The long-drided Lamarckian theory that organisms can pass on acquired characteristics to their offspring has been proven correct by the discoveries of Steele and his colleagues regarding the immune system.
(B) Steele and his colleagues have devised an account of a mechanism by which acquired characteristics could be passed on to an organism's offspring, and they claim to have found evidence for the operation of this Larnarckian mechanism.
(C) Although Steele and his colleagues have succeeded in showing that changes that occur in the immune system can be passed on to offspring, it is unlikely that a similar mechanism operates elsewhere in the body.
(D) In contrast to the standard theory of evolution, the claims of Steele and his colleagues that organisms can pass on acquired characteristics to their offspring are highly speculative and rest on purely circumstantial evidence.
(E) By showing that RNA can revert back into DNA, Steele and his colleagues have removed the main obstacle to general acceptance of the Lainarckian hypothesis that organisms can pass on acquired characteristics to their offspring.


2. The author most likely calls a certain kind of mutation a "typo" (line 25) primarily in order to

(A) distinguish it from mutations that are adaptive
(B) characterize it as relatively inconsequential
(C) indicate that it is an instance of imperfect copying
(D) emphasize that it is easily overlooked
(E) suggest an analogy between scientific investigation and textual analysis


3. The passage most strongly suggests that the author has which one of the following attitudes toward the theory proposed by Steele and his colleagues?

(A) confidence in its truth
(B) indignation at its divergence from Darwinism
(C) distrust of its novelty
(D) doubt concerning its plausibility
(E) dismay at its lack of rigor


4. The passage is primarily concerned with

(A) offering a historical account of the development of an evolutionary theory
(B) describing the efforts of a modem biologist to vindicate a long-disregarded evolutionary theory
(C) answering a set of questions about the immune system in light of evolutionary theory
(D) evaluating the overall merits of an evolutionary theory that has been rejected by most modem biologists
(E) presenting a discredited evolutionary theory as a case study in the philosophy of science


5. What is the primary function of the last paragraph in the structure of the passage as a whole?

(A) to present various objections that have been raised against the neo-Lamarckian theory outlined in the preceding paragraphs
(B) to dismiss the neo-Lamarckian theory outlined in the preceding paragraphs as not being supported by evidence
(C) to explain how the neo-Lamarckian theory outlined in the preceding paragraphs could be revised to take new findings into account
(D) to suggest several possible directions for further research regarding the neo-Lamarckian theory outlined in the preceding paragraphs
(E) to indicate the nature of the evidence for the neo-Larnarckian theory outlined in the preceding paragraphs


6. The passage most strongly suggests that the author would agree with which one of the following statements?

(A) Contrary to the opinion of most modern biologists, certain acquired characteristics probably can be passed on from one generation to the next.
(B) Steele and his colleagues have not actually observed the process of reverse transcription in immune cells.
(C) The patterns of mutations concentrated in particular areas of genes that carry instructions for immune system responses indicate that the DNA in these genes has been altered by a virus.
(D) The passing on of acquired characteristics from one generation to the next, if it occurs at all, is probably confined to the immune system.
(E) Unless a hypothesis can be confirmed by direct observation, it should be regarded as speculation rather than as science.


7. Which one of the following, if true, would most strengthen the position attributed to Steele and his colleagues in the passage?

(A) Scientists have succeeded in altering the 13NA in reproductive cells of laboratory mice by introducing a virus carrying new DNA.
(B) The patterns of mutations found in the genes that carry instructions for immune system responses are also found in genes in the nervous system.
(C) The process by which the immune system tests out the efficacy of cellular mutations is one of random trial and error.
(D) Fossil remains show that giraffes gradually evolved with increasingly long necks.
(E) It is known that birds can pass on acquired immunities to their gestating chicks via the yolk sacs in their eggs.


8. Suppose a scholar believes that the surviving text of a classical Greek play contains alterations introduced into the original text by a copyist from a later era. Which one of the following pieces of evidence bearing upon the authenticity of the surviving text is most analogous to the kind of evidence mentioned in the last paragraph of this passage?

(A) a copy of the original, unaltered text discovered in a manuscript independently known to date from the classical period
(B) a letter in which the copyist admits to having altered the original text in question
(C) an allegation by one of the copyist's contemporaries that the copyist altered the original text
(D) an account dating from the playwright's time of a performance of the play that quotes a version of the text that differs from the surviving version
(E) vocabulary in the surviving text that is typical of the later era and not found in other texts dating from the classical period