lsat 5-2-23

23. “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.

答案我选的也是C，可是对C我有一点疑惑，C的意思是不是说在有一些种族里指纹特征是一样的啊？可是平时的知识不是说每个人的指纹都不一样吗？？？？？？？？

Fist of all, DNA finger printing is not same as finger prints. The name just uses an anlogy to show that DNA can be matched like finger prints.

Conclusion: "Proponents have claimed astronomically high odds against obtaining a match by chance alone."

                       in another words: DNA pattern is very unlikely to be matched by chance(i.e. two different people's DNA patten are matched accidentally)

Assumption:  "there is independence between the different characteristics represented by a single pattern.> ">

>                  in another words: everybody has different DNA pattern because of different characteristics. >

>Only C) attacks the assumption directly by showing some subgroups might share same genetic characteristics. Other choices, only B has some merit, but it does not attack the assumption directly. >