Why is PCR a necessary step in the analysis of a DNA sample taken from a crime scene A: the sample yields very little DNA B: the sample may be contaminated C: the sample undergoesdegradation D: the sample may not provide an accurate sequence

The answer is A. The sample from a crime scene does not have enough DNA to perform forensics tests such as DNA matching. PCR - polymerase chain reaction - is used to amplify the DNA to required amount. Each cycle of PCR amplifies DNA two-folds