gautrang wrote:
“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.
(B) There is generally accepted theoretical basis for interpreting the patterns produced by the procedure.
(C) In the whole population there are various different subgroups, within each of which certain sets of genetic characteristics are shared.
(D) The skill required of laboratory technicians performing the DNA fingerprinting procedure is not extraordinary.
(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.
Source: LSAT
I arrived at the answer purely by POE, could anybody please explain to me the argument and the logic. Thanks.
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?