Polymerase chain reaction (PCR) is used to examine and trace the spread of infectious disease within a population. It can be used to detect bacterial or viral DNA in blood samples, water or food supplies , or other locations in the environment.

With PCR, any specific segment ( target sequence) in a DNA sample can be copied many times within a test tube. The process of PCR is depicted in figure 1:

Figure 1: PCR requires double-stranded DNA containing the target sequence , a heat- resistant DNA polymerase, all four nucleotides, and two 15- to 20-nucleotide single DNA strands that serve as primers .

One primer is complementary to one end of the target sequence on one strand; the second primer is complementary to the other end of the sequence on the other strand. a.

Describe the biological process depicted in the steps of the PCR model . b. Explain the relationship between the primers and DNA polymerase in the model .

Explain why DNA polymerase must be heat resistant during the PCR process. c. The target DNA sequence used in the PCR process is CCCGTTAAG .

Represent the complementary nucleotide sequence that will add to the 3′ end of the DNA primer . d. Identify the eukaryotic cell location of the biological process described in

(a). Explain why this biological process occurs at this location , as opposed to another within the cell.

Image transcription text

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