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# New research by Paul Fildes and K. Whitaker

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New research by Paul Fildes and K. Whitaker  [#permalink]

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Updated on: 21 Aug 2018, 18:45
2
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based on 266 sessions

78% (03:16) correct 22% (03:30) wrong

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Question 2
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63% (01:28) correct 37% (01:51) wrong

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New research by Paul Fildes and K. Whitaker challenges the theory that strains of bacteria can be “trained” to mutate by withholding a metabolite necessary for their regular function. In particular, they consider the case of bacteria typhosum, which needs tryptophan in order to reproduce. Earlier researchers had grown the bacteria in a medium somewhat deficient in tryptophan and observed the growth of mutant strains of the bacteria which did not need tryptophan in order to reproduce.

Fildes and Whitaker argue that the withholding of tryptophan did not induce these mutant strains of bacteria. Rather, these mutants were already present in the original sample of bacteria typhosum, albeit in a concentration too small to detect. In experimenting with the bacteria grown in agar cultures, they found that by plating out huge quantities of the bacteria, one could locate mutant strains. Because of the possibility that the lack of uniformity of the agar cultures had in fact trained mutant strains, they conducted similar experiments with liquid cultures and again found that mutant strains of the bacteria were present in the original sampling. From these experiments, Fildes and Whitaker conclude that the mutants are of genetic origin and are not induced by environmental training. They asserted that the concentration of tryptophan is unrelated to the appearance of these mutants in the bacteria.

To confirm these results, Fildes and Whitaker used an innovative plating technique using pile fabrics, such as velvet or velveteen, to accurately imprint the growth found on an original agar plate to a series of replica agar plates. The process entails taking the original agar plate, inverting it onto the velvet while using light finger pressure to transfer growth, and then imprinting the fabric, with its pattern of growth, on the new agar plates. By using this replica plating method, Fildes and Whitaker demonstrated that the mutants were in fact genetically present or preadapted, as the locations of the mutant strains of bacteria on the replica plates were identical to the locations of the mutant strains on the original agar plate.

1. According to the passage, Fildes and Whitaker conducted the experiment with liquid culture because

A. agar culture contained tryptophan
B. liquid culture allowed for easier plating
C. agar culture could not support a sufficiently large number of bacteria
D. liquid culture offered a more consistent medium
E. agar culture did not adhere well to pile fabric

2. It can be inferred from the passage that the replica plating method is effective for which of the following reasons?

A. It allows researchers to determine the relative sizes of different populations of bacteria.
B. It shows that no new mutant strains developed after transfer from the original agar plate.
C. It eliminates the possibility that the agar culture was contaminated by a different type of bacteria.
D. It demonstrates that no tryptophan was present in the original agar culture.
E. It establishes that the original agar culture contained the necessary metabolites for bacterial reproduction.

3. Which of the following most accurately states the purpose of the passage?

A. To defend a scientific hypothesis from attack by an innovative technique
B. To describe a process by which bacteria can be trained to mutate
C. To present the results of an experiment designed to test an established theory
D. To argue against an established protocol on the grounds that it is outdated
E. To challenge a scientific technique used to prove a questionable theory

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Originally posted by Skywalker18 on 08 Sep 2016, 01:32.
Last edited by workout on 21 Aug 2018, 18:45, edited 2 times in total.
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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08 Sep 2016, 01:33

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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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08 Sep 2016, 01:34
6 mins 40 seconds , including 2 mins 50 seconds to read
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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08 Sep 2016, 06:19
8 mins. DBC

Can someone please explain how can we reject choice E in question 2?
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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08 Sep 2016, 21:24
Top Contributor
7 mins all correct. Nice passage.
Regarding the query on Q2, why not E.

It can be inferred from the passage that the replica plating method is effective for which of the following reasons?
E) It establishes that the original agar culture contained the necessary metabolites for bacterial reproduction.

2:Fildes and Whitaker argue that the withholding of tryptophan did not induce these mutant strains of bacteria. Rather, these mutants were already present...Blah Blah
P3: To confirm these results, Fildes and Whitaker used an innovative plating technique using pile fabrics

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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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09 Jan 2018, 08:30
3min 58 sec for passage
3 min 24 sec for 3 questions
got ques 2 wrong , 2/3 correct
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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09 Jan 2018, 08:52
1
abhimahna wrote:
8 mins. DBC

Can someone please explain how can we reject choice E in question 2?

May be its not required now - as you have already passed this phase.

By using this replica plating method, Fildes and Whitaker demonstrated
that the mutants were in fact genetically present or preadapted, as the locations of the mutant strains of bacteria on the replica plates were identical to the locationsof the mutant strains on the original agar plate.

Means => mutant did not develop after the transfer=> mutants were in fact genetically present or preadapted
B says this -> no new mutant strains developed after transfer from the original agar plate.

Lets see E-> It establishes that the original agar culture contained the necessary metabolites for bacterial reproduction.
outside info.

Anyways correct me- if you think my reasoning is wrong.
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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01 Aug 2018, 06:50
Can someone explain why answer choice E is wrong for question 3?

In first paragraph - Earlier researchers had grown the bacteria in
a medium somewhat deficient in tryptophan and observed the growth of mutant strains of the bacteria which did not need tryptophan in order to reproduce.

Fildes and Whitaker argue that the withholding of tryptophan did not induce these mutant strains of bacteria. Rather, these mutants were already present in the original sample of bacteria typhosum....

Later Fildes & Whitaker used innovative techniques to prove their point..
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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21 Aug 2018, 10:14
SWAT09 wrote:
Can someone explain why answer choice E is wrong for question 3?

In first paragraph - Earlier researchers had grown the bacteria in
a medium somewhat deficient in tryptophan and observed the growth of mutant strains of the bacteria which did not need tryptophan in order to reproduce.

Fildes and Whitaker argue that the withholding of tryptophan did not induce these mutant strains of bacteria. Rather, these mutants were already present in the original sample of bacteria typhosum....

Later Fildes & Whitaker used innovative techniques to prove their point..

The answer to your question is probably that Fildes and Whitaker did not challenge the technique used by the previous researchers,
they challenged the result or conclusion of that experiment.

Overall the answer choices are controversial for the third question, I hope someone will explain it more thoroughly.
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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22 Aug 2018, 20:11
5 minutes: all correct

1. D
Because of the possibility that the lack of uniformity of the agar cultures had in fact trained mutant strains
2. B
Fildes and Whitaker demonstrated that the mutants were in fact genetically present or preadapted
this means no new mutant strains were developed after transfer from the original agar plate. hence B
3. C
The passage begins by Paul Fildes and K. Whitaker challenging the older theory and subsequent passages explores more into their scientific approach and challenging the old theory
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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27 Aug 2018, 02:36
7:32 min total
2 out of 3 correct
Can any one explain 2 Qn ?
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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09 Sep 2018, 07:31
mayursurya wrote:
7:32 min total
2 out of 3 correct
Can any one explain 2 Qn ?

Check Highlighted Part of Passage-2 and Passage-3. YOU will get answer of questions-2.

From these experiments, Fildes and Whitaker conclude that the mutants are of genetic origin and are not induced by environmental training. They asserted that the concentration of tryptophan is unrelated to the appearance of these mutants in the bacteria.

To confirm these results, Fildes and Whitaker used an innovative plating technique using pile fabrics, such as velvet or velveteen, to accurately imprint the growth found on an original agar plate to a series of replica agar plates. The process entails taking the original agar plate, inverting it onto the velvet while using light finger pressure to transfer growth, and then imprinting the fabric, with its pattern of growth, on the new agar plates. By using this replica plating method, Fildes and Whitaker demonstrated that the mutants were in fact genetically present or preadapted, as the locations of the mutant strains of bacteria on the replica plates were identical to the locations of the mutant strains on the original agar plate.
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Re: New research by Paul Fildes and K. Whitaker  [#permalink]

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03 Feb 2019, 09:27
Can somebody please explain why is Q3 E not correct?
Based on the last para of the first passage. It is indeed challenging the scientific technique used by the previous researchers.
Re: New research by Paul Fildes and K. Whitaker   [#permalink] 03 Feb 2019, 09:27
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