PT3.S2.Q23 - DNA fingerprinting

Lizardking-1

Can someone explain their reasoning for the right answer? I have a general intuition as to why this is correct, but am having a difficult time articulating it to myself. Thanks so much! #HELP

McBeck418

I'm not sure if this is helpful, because I don't really understand exactly what the last sentence is supposed to mean specifically, but I took it to mean something like high variance. Based on that, we are told that finding a DNA match is nearly impossible to do by chance because of this high level of variance (the independence between characteristics represented by a pattern). If we could narrow that down, perhaps, by grouping characteristics together among a group of people, we could bring down the 'astronomically high odds against' using chance because now we can more easily pinpoint who the person might be.

So C weakens the assertion that we need to use this new DNA fingerprinting process because the odds of finding it by chance are astronomically high.

LivinLaVidaLSAT

Here's how I thought through this one. Let me know if you had similar/different thoughts about C.

Conclusion (Proponents):The odds are very high it’s not likely to get a match just by chance.

Premise (Assumption): Each part of the pattern is independent.
What does this mean? No element always shows up with another part of the pattern; they are not dependent. Think in terms of sufficient and necessary. If you have one characteristic, you’re guaranteed to have the other. I really had to think about how to translate the last sentence.

Prephrase: Didn’t have one. Just knew what I was looking for. Since we’re given the assumption (how nice), my thought was they want us to weaken this by attacking the assumption. I want an answer that shows the characteristics aren’t as independent as the proponents think.

(C) Yes. If subgroups share some sets of genetic characteristics, you will get multiple people with patterns that match up in various spots. This leans towards possibly finding a match by chance.

Wrong answers:
(A) Maybe strengthen. Ignores the genetic material everyone shares which would mean seeing the many of the same pattern pieces for everyone. This answer makes it more likely they’re analyzing independent characteristics in a pattern which reduces the chance of match by chance.

(B) No effect. Doesn’t address the assumption. The theory behind interpreting the patterns doesn’t determine whether pattern elements are dependent/independent.

(D) No effect. Doesn’t relate to the assumption. This would not affect whether or not there is independence.

(E) No effect. Can’t relate tracing the transmission of diseases to the pattern odds. It also bothers me that this answer says the techniques used in DNA fingerprinting instead of just saying they used DNA fingerprinting. These two phrases mean different things to me. I think this is open for interpretation.