Question

Part A: Describe what PCR is ( not just the definition, but what is being done)

Part B: Explain how crime scene investigators can identify individuals who left even tinu traces of DNA at a crime scene. Hint: a complete answer will discuss both PCR and how a DNA sample can be matched to a particular person!

Answer 1

Part A)

PCR stands for polymerase chain reaction. This technique is uest to amplify the DNA fragment. We add taq DNA polymerase, primers, nucleotides, buffer containing magnesium ions.

It includes three steps:

* Denaturation: The 93-95°C temperature is required at this step. This leads to denature the ds DNA.

* Annealing: This requires 59-70°C. This leads to annealing of the primer to the template strands.

* Extension: DNA polymerase leads to synthesize the new DNA via adding nucleotide on the primer.

Part B)

In this case, we obtain the sample from the crime scene and from the suspected ones. The DNA from bothe suspected ones and crime scene samples are amplified in the PCR.

Then this amplified DNA are run on the gel electrophoresis.

* Now the DNA fragments are separated on the basis of their fraents length. The shorter fragments run faster as comoared to the longer ones.

* Now observe the band pattern between the crime scene and suspectes one samples. If there is found exact match of bands between them, this suggests that suspected person hase done the crime.

But if there is not found all band matches betwen the crime and suspected ones, then this suggests that crime is not done by the suspected one.