Research directed toward recovering ancient DNA began in 1984, when

Question

﻿Research directed toward recovering ancient DNA began in 1984, when pieces of DNA were extracted from museum specimens of an animal extinct for about a century. Most such genetic material recovered from biological relics consists of tiny fragments, rather than the strings of thousands of molecules typically found in living organisms, but these fragments may contain sufficient information to identify a species through comparison with modern DNA from descendant species. However, the need to verify whether particular fragments actually come from ancient organisms or whether they come from modern contaminants, such as the sweat of people who have handled the specimens, is crucial. For example,  some scientists  claim to have extracted DNA fragments from 17-million-year-old magnolia leaves found in an unusual fossil deposit in Idaho. But  other scientists  suggest that this DNA is a modern contaminant; they argue that even under the most favorable conditions, the rate of degradation of DNA is such that useful genetic material could not be recovered from fossils that old and that since the leaves were trapped in wet deposits, it is particularly unlikely that any DNA would have survived so long. A solution to this debate lies in the fact that any ancient DNA should differ from that of related modern species. If the DNA extracted from the fossil leaves were actually a modern contaminant, this fact would be apparent from the information contained in the DNA.   1 ﻿
 1. The passage is primarily concerned with

A. questioning the applicability of a particular methodology
B. identifying issues central to correctly dating DNA fragments
C. presenting evidence to undermine a theory about the age of certain biological relics 
D. describing two methods commonly used to date certain biological relics
E. presenting several possible explanations for the survival of DNA in biological relics

2 
﻿ 2. Which of the following statements, if true, would most clearly undermine the usefulness of the author's solution to the scientists' debate that is discussed in the passage?

A. DNA extracted from ancient specimens is not identical to the DNA of related modern species.
B. Most ancient biological relics are not preserved under favorable conditions.
C. Only tiny fragments of genetic material can be recovered from ancient biological relics.
D. There are many segments of DNA that show very little change between ancient and modern DNA.
E. Careless handling of biological relics is an ongoing problem in attempts to extract ancient DNA from fossils.

3 ﻿
 3. The passage suggests that the scientists mentioned in the first highlighted portion of text differ from the scientists mentioned in the second highlighted portion of text in that the former

A. assume a higher rate of degradation of DNA in fossil material
B. argue that the conditions of the Idaho fossil deposit were exceptional
C. have different techniques for extracting genetic material from a specimen that is 17 million years old
D. have devised a method for identifying modern contaminants found in biological relics
E. believe that fragments of DNA could survive in fossils for 17 million years

Another set of question on the same passage is  HERE .

YB114 · Answer

Sir, Please post official explanation of all questions.

Sajjad1994 · Answer

Explanation

1. The passage is primarily concerned with

Difficulty Level:   Medium

Explanation

Option (B)   is the correct answer because the passage primarily discusses the challenges and issues associated with accurately dating DNA fragments extracted from ancient biological relics. The passage talks about the difficulty of determining whether the DNA fragments come from ancient organisms or modern contaminants, and it emphasizes the importance of verifying the age of these fragments. This central theme revolves around the dating and authenticity of DNA fragments, making  option (B)  the most accurate choice.

A.  The passage doesn't primarily focus on questioning the applicability of a specific methodology. While it discusses the need to verify the source of DNA fragments, it's not concerned with challenging the methodology itself.

C.  This option is close but not entirely accurate. The passage does present evidence and arguments to undermine the theory that 17-million-year-old DNA fragments are authentic, but its primary focus is on the challenges of dating these fragments rather than explicitly aiming to undermine a theory.

D.  The passage does mention the need to verify the age of DNA fragments, but it doesn't describe two specific methods for dating biological relics. Instead, it discusses the difficulties associated with dating ancient DNA fragments.

E.  The passage briefly touches upon the idea that DNA from ancient organisms should differ from modern species' DNA, but it doesn't present several possible explanations for the survival of DNA in biological relics. The primary concern is verifying the age of these DNA fragments.

Answer: B

Sajjad1994 · Answer

Explanation

2. Which of the following statements, if true, would most clearly undermine the usefulness of the author's solution to the scientists' debate that is discussed in the passage?

Difficulty Level:   Medium

Explanation

The author's solution to the scientists' debate is based on the premise that ancient DNA should differ from that of related modern species. The idea is that if the DNA extracted from ancient specimens is significantly different from the DNA of related modern species, it would suggest that the extracted DNA is not a modern contaminant and is indeed ancient. Therefore, to undermine the usefulness of the author's solution, we need to find a statement that challenges this premise.

A.  This statement supports the author's solution by reinforcing the idea that ancient DNA should differ from modern DNA. It does not undermine the solution.

B.  This statement does not directly address the difference between ancient and modern DNA, which is the core of the author's solution. It focuses on preservation conditions instead.

C.  This statement is mentioned in the passage but doesn't directly challenge the premise that ancient DNA should differ from modern DNA. It addresses the limitations of DNA recovery but not the core argument.

D.  This statement directly undermines the author's solution. If many segments of DNA show little change between ancient and modern DNA, it suggests that the DNA extracted from ancient specimens might not necessarily differ significantly from that of related modern species, weakening the argument.

E.  This statement relates to the potential contamination of DNA but does not address the core premise about the difference between ancient and modern DNA.

So,  option (D)  is the correct choice because it most clearly undermines the author's solution by suggesting that there are many segments of DNA that show very little change between ancient and modern DNA, potentially making it difficult to differentiate between ancient DNA and modern contaminants based on the differences in the DNA sequences.

Answer: D

Sajjad1994 · Answer

Explanation

3. The passage suggests that the scientists mentioned in the first highlighted portion of text differ from the scientists mentioned in the second highlighted portion of text in that the former

Difficulty Level:   Easy

Explanation

A.  This option is not supported by the passage. Both groups of scientists acknowledge the rate of degradation of DNA in fossils. The first group believes that they have successfully extracted ancient DNA, while the second group questions the feasibility of DNA surviving for 17 million years. Therefore, both groups acknowledge the challenges of DNA degradation.

B.  The passage does not provide information about the conditions of the Idaho fossil deposit being exceptional. Both groups of scientists may have differing opinions about the conditions, but this is not explicitly mentioned in the passage.

C.  The passage does not indicate that the two groups of scientists have different techniques for extracting genetic material. The difference lies in their beliefs about the authenticity of the extracted DNA, not in their methods of extraction.

D.  The passage does not suggest that either group has devised a specific method for identifying modern contaminants. Both groups discuss the need to verify whether DNA fragments come from ancient organisms or modern contaminants, but neither group is presented as having a unique method for this purpose.

E.  This option accurately reflects the key difference between the two groups of scientists as presented in the passage. The first group believes that ancient DNA fragments can survive for 17 million years, while the second group questions this belief and suggests that it is unlikely for DNA to have survived for such a long time. Option E aligns with the information provided in the passage and is the correct answer.

Answer: E

GarvitGoel · Answer

Hi BB & Bunuel,

While attempting the official mock there were 3 new questions which appeared on that mock regarding this particular RC, which are not updated on GMAT club.

Requesting you to please update as well.

PFA the SS.

Bunuel · Answer

Posted that question  HERE . Thank you!

egmat · Answer

Question 2

Let's break this down together - this is actually a great example of how to approach "undermine" questions in Reading Comprehension.

Here's how I'd think through this step by step:

Step 1: Identify the Author's Solution 
The passage tells us the author's proposed solution to the contamination debate:  "any ancient DNA should differ from that of related modern species."  So if scientists find DNA that's identical to modern species, it's probably contamination. If it's different, it might be genuinely ancient.

Step 2: Ask "What Would Make This Solution Useless?" 
For this solution to fail, we'd need something that makes it impossible to reliably distinguish ancient DNA from modern DNA through comparison. Think about it - if you can't tell them apart, the whole method breaks down.

Step 3: Evaluate Each Choice 
Let's focus on the key ones:
- Choice A actually  supports  the solution by confirming that ancient and modern DNA are different
- Choice D says "many segments of DNA show very little change between ancient and modern DNA" - this directly attacks the solution's foundation

Step 4: Why D Undermines the Solution 
If ancient and modern DNA segments are too similar to distinguish reliably, then the author's comparison method becomes unreliable. You couldn't confidently say whether DNA is ancient or contaminated because they'd look nearly identical. This makes the proposed solution essentially useless.

The key insight here is recognizing that the solution depends entirely on detectable differences. Remove those differences, and the whole approach collapses.

You can check out the  comprehensive passage analysis and systematic approach on Neuron by e-GMAT  to master these "undermine the solution" RC patterns. You can also explore detailed solutions for  similar official RC questions with advanced frameworks  for consistent accuracy across all RC question types.

Research directed toward recovering ancient DNA began in 1984, when

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GMAT Reading Comprehension (RC) Questions

Research directed toward recovering ancient DNA began in 1984, when

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards