“DNA fingerprinting” is a recently-introduced biochemical procedure th

Think of what you have to weaken here: the claim of the proponents of DNA fingerprinting. What is that claim? that odds against obtaining a match by chance alone are astronomical. Say, the odds are something like a 1 in a billion that the DNA fingerprint of one person will match the DNA fingerprint of another person.

You have to weaken this claim. The author tells you that the odds were calculated assuming that the different characteristics in a pattern are independent. Think of a password. If you have to write a 10 letter password using only letters of the alphabet, there are 26*26*26.....26 = (26)^10 different ways in which you can write it. The odds against two people creating the same password are very high. You are assuming here that each letter is independent of the other 9 letters. What if that is not the case? Say, your password must have at least 2 of the 5 vowels. You have created restrictions. Each letter is not independent of the other letters now. The number of passwords you can create now is significantly lower.

Option (C) tells you that some groups share the same characteristics i.e. of the 10 letters, 5 letters are identical in each password of this group. Now, the chances of getting the same password have increased significantly. This weakens the claim that the odds against finding a match are very high.

The only other option you could get stuck in is (A) The large amount of genetic material that people share with all other people and with other animals is not included in the DNA fingerprinting procedure.
This just tells you that the features that people share are not a part of fingerprinting procedure. This is like telling you that the passwords actually have 15 letters but the first 5 letters are the same for everyone. Basically, it doesn't change our odds at all. We anyway did not include the common part in our calculation. Hence, this option does not weaken the claim.

We need to find a fact which weakens the claim that DNA fingerprinting is foolproof. It is also mentioned that 'These odds are based on an assumption that there is independence between the different characteristics represented by a single pattern.'

(C) In the whole population there are various different subgroups, within each of which certain sets of genetic
characteristics are shared.
This information clearly weaken the claim. As different subgroups may share the same genetic characteristics, the assumption on which the claim is based is proved wrong.

First POE is not too bad. IMO you should look at all answers to see that there is no "better" answer, so you can POE while you do that. A better answer is an answer that attack directly the conclusion (in weaken question like this) and adds less "out of scope" data as possible.
When I looked at this question I immediately canceled A,B & D as IMO they are too far from the data given in the question or simply irrelevant.
When I looked at E it seemed to attack less directly the "independence between the different characteristics represented by a single pattern" than C did. so I was left with C.
Hope that helps..

Out of the 5 choices only A and E are relevant to the premises provided in the stimulus.

Option A strengthens or supports the proponents by discounting the common genetic material shared.

Option C is exactly the opposite of option A and it weakens the argument presented in the stimulus.

And I agree, POE is the best technique here.

I thought in A, the answer means that some parts of the DNA is not tested, and therefore it's most likely to cause mistakes.

Option A talks of some parts which is shared across diverse groups and hence including it in the DNA analysis will skew the result. Hence option A should be ruled out.

The idea is to cut out the common portion and retain the uniqueness of the DNA fingerprint to uniquely identify the individual.


Side note: I have heard that comparing at least 6 different areas of the DNA strands or sequences, the chances of these 6 areas matching for any two individual is simply out of the question since the chances are less than 1 in 6 billion.

Completely irrelevant to the current context but nevertheless interesting bits of information.

Used POE to eliminate B, D & E since they are irrelevant

Assumption is based on the fact that there is independence between the different characteristics represented by a single pattern. Therefore, anything that suggests that there is no independence between the different characteristics will weaken this assumption. Between A & C, A talks about the material that is shared and is not included in the fingerprinting procedure. Not much help. However, C talks about the fact that different subgroups share certain genetic characteristics.

The basic assumption that the proponents consider is the independence between the different characteristics; therefore we need to attack this basic assumption by finding something that will show us that the patterns were similar and not unique/independent.

A- if it is not included in the procedure that means the patterns are still independent.
b- not relevant
C- YES , there are groups, which share genetic characteristics : attacks the basic assumption of independent characteristics
D- skills required ? Out of scope
E- talks about diseases , strike it off .

Arrive at

we need to get an answer choice that would support usage of dna fingerprinting.
the proponents say it will be difficult..we need to say it will be not..
A - that makes the usage difficult so out
B - completely irrelevant
C - ok, so the patterns CAN be classified..we can use the technique to ID the suspect..because it will belong to a specific subgroup.
D - what techniques dna fingerprinting uses and how difficult these are are irrelevant.
E - good one...but one large family "shares" the same genetic code..we need an answer choice that would say that different genetic codes can be classified into subgroups/identified. so e is out and C stands

We want an answer choice that gives a reason why the assumption that "independence between different characteristics" in a single pattern does NOT mean it's unlikely to get a match by mere chance. If this seems too complicated, we can just think of it as: we want a reason why the DNA of a suspect and the DNA found at a crime scene could match up due to chance, not because it's the actual culprit's DNA. (C) offers the possibility that people in subgroups share the same genetic characteristics that show up in the patterns.

(A) perhaps strengthens the argument. If we're worried about seeing patterns because we all largely have the same genes, (A) eliminates this possibility.
(B) is out of scope. We aren't concerned with theories of interpretation but the odds of a mistake. If anything, (B) may actually strengthen the argument--we're all pretty confident in the best way of interpreting, so if there's a mistaken match, we'll catch it!
(D) the skill required is not extraordinary? That's good, that means they can be low skilled and still do the job! Regardless, this is out of scope. It doesn't address the link between the patterns and the accuracy.
(E) is irrelevant. Great, they've helped with disease research. What does this have to do with odds?
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This is a bit of a wordy passage, particularly the second sentence. Essentially what proponents of DNA fingerprinting are saying is that the results obtained from the biochemical procedure are valid and that chance can be ruled out.

We need a weakener that attack the idea that a person's generic material can be used to reliably match a suspect's genetic material against that of a specimen from the crime scene.

“DNA fingerprinting” is a recently-introduced biochemical procedure that uses a pattern derived from a person’s genetic material to match a suspect’s genetic material against that of a specimen from a crime scene. Proponents have claimed astronomically high odds against obtaining a match by chance alone. These odds are based on an assumption that there is independence between the different characteristics represented by a single pattern.

Which one of the following, if true, casts the most doubt on the claim of the proponents of DNA fingerprinting?


(A) The large amount of genetic material that people share with all other people and with other animals is not included in the DNA fingerprinting procedure. X
This would appear to strengthen the argument because it tells us that extraneous noise (scientific jargon for confounding) is not included in the procedure. As a result, we would have greater confidence in the results.

(B) There is generally accepted theoretical basis for interpreting the patterns produced by the procedure. X
Again, this seems to strengthen

(C) In the whole population there are various different subgroups, within each of which certain sets of genetic characteristics are shared.
CORRECT. "...certain sets of genetic characteristics are shared" spells trouble for the argument...see the justification in A)

(D) The skill required of laboratory technicians performing the DNA fingerprinting procedure is not extraordinary. X
Irrelevant.

(E) In the investigation of certain genetic diseases, the techniques used in DNA fingerprinting have traced the transmission of the diseases among the living members of very large families. X
Irrelevant.
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