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• This can help them select high-risk candidates for colon cancer tests. Researchers have also
detected potentially metastatic cells in the circulation of patients with newly diagnosed tumors.

• PCR can even diagnose the diseases of the past. Former vice president and presidential
candidate Hubert H. Humphrey underwent tests for bladder cancer in 1967.

• Although the tests were negative, he died of the disease in 1978. In 1994, researchers
compared a 1976 tissue sample from his cancer-ridden bladder with his 1967 urine sample.
With the help of PCR amplification of the small amount of DNA in the 27-year-old urine, they
found identical mutations in the p53 gene, well known for suppressing tumors, in both
samples.

DNA fingerprinting

• PCR’s power at identifying individual genetic makeup has made it invaluable for use in
paternity testing.

• By amplifying specific DNA fragments from parents or close relatives, it is possible to
reconstruct relatedness between individuals.

• PCR can not only identify relationships between people today, but can also be used to
identify historical family relationships!

PCR and Genetically-modified foods

• Genetically-modified foods (GMO foods) are widely grown in the USA and other countries.

• For various reasons, some countries require exporters to indicate the percentage of GMO
content in grain and food shipments.

• PCR can be used to accurately measure the exact quantity of genetically-modified food in a
shipment, by “looking” at the DNA that makes up the food!

Further applications of PCR

• Genotyping.

• Mutagenesis.

• Sequencing.

• Genetic engineering.